Deleted 'Glossary View' by mistake D8
If you are exporting and importing your configuration, you can simply re-import config from your last export. If you are not doing that already, you should definitely learn how to do so.

If you don't have the view exported, one way to get it back is to create another Drupal 8 site in your local development environment and then go to the config single export page (/admin/config/development/configuration/single/export) and choose Configuration type View and Configuration name Glossary.

Then go to your other site and choose "Import" and import the code.

For reference, here is my export (Drupal 8.4-rc2):

uuid: 350860b2-753f-4774-b504-5cc14b62c099
langcode: en
status: false
dependencies:
  config:
    - system.menu.main
  module:
    - node
    - user
_core:
  default_config_hash: '-pCFOVfbt__jaohFffTLnVavh4OBC6CjREAnchiRomQ'
id: glossary
label: Glossary
module: node
description: 'All content, by letter.'
tag: default
base_table: node_field_data
base_field: nid
core: '8'
display:
  default:
    id: default
    display_title: Master
    display_plugin: default
    position: 0
    display_options:
      query:
        type: views_query
        options:
          query_comment: ''
          disable_sql_rewrite: false
          distinct: false
          replica: false
          query_tags: {  }
      use_ajax: true
      access:
        type: perm
        options:
          perm: 'access content'
      cache:
        type: tag
        options: {  }
      exposed_form:
        type: basic
        options:
          submit_button: Apply
          reset_button: false
          reset_button_label: Reset
          exposed_sorts_label: 'Sort by'
          expose_sort_order: true
          sort_asc_label: Asc
          sort_desc_label: Desc
      pager:
        type: mini
        options:
          items_per_page: 36
          offset: 0
          id: 0
          total_pages: 0
          expose:
            items_per_page: false
            items_per_page_label: 'Items per page'
            items_per_page_options: '5, 10, 25, 50'
            items_per_page_options_all: false
            items_per_page_options_all_label: '- All -'
            offset: false
            offset_label: Offset
          tags:
            previous: ‹‹
            next: ››
      fields:
        title:
          id: title
          table: node_field_data
          field: title
          plugin_id: field
          relationship: none
          group_type: group
          admin_label: ''
          label: Title
          exclude: false
          alter:
            alter_text: false
            text: ''
            make_link: false
            path: ''
            absolute: false
            external: false
            replace_spaces: false
            path_case: none
            trim_whitespace: false
            alt: ''
            rel: ''
            link_class: ''
            prefix: ''
            suffix: ''
            target: ''
            nl2br: false
            max_length: 0
            word_boundary: true
            ellipsis: true
            more_link: false
            more_link_text: ''
            more_link_path: ''
            strip_tags: false
            trim: false
            preserve_tags: ''
            html: false
          element_type: ''
          element_class: ''
          element_label_type: ''
          element_label_class: ''
          element_label_colon: true
          element_wrapper_type: ''
          element_wrapper_class: ''
          element_default_classes: true
          empty: ''
          hide_empty: false
          empty_zero: false
          hide_alter_empty: true
          entity_type: node
          entity_field: title
        name:
          id: name
          table: users_field_data
          field: name
          label: 投稿者
          relationship: uid
          plugin_id: field
          type: user_name
          group_type: group
          admin_label: ''
          exclude: false
          alter:
            alter_text: false
            text: ''
            make_link: false
            path: ''
            absolute: false
            external: false
            replace_spaces: false
            path_case: none
            trim_whitespace: false
            alt: ''
            rel: ''
            link_class: ''
            prefix: ''
            suffix: ''
            target: ''
            nl2br: false
            max_length: 0
            word_boundary: true
            ellipsis: true
            more_link: false
            more_link_text: ''
            more_link_path: ''
            strip_tags: false
            trim: false
            preserve_tags: ''
            html: false
          element_type: ''
          element_class: ''
          element_label_type: ''
          element_label_class: ''
          element_label_colon: true
          element_wrapper_type: ''
          element_wrapper_class: ''
          element_default_classes: true
          empty: ''
          hide_empty: false
          empty_zero: false
          hide_alter_empty: true
          entity_type: user
          entity_field: name
        changed:
          id: changed
          table: node_field_data
          field: changed
          label: 前回の更新
          type: timestamp
          settings:
            date_format: long
            custom_date_format: ''
            timezone: ''
          plugin_id: field
          relationship: none
          group_type: group
          admin_label: ''
          exclude: false
          alter:
            alter_text: false
            text: ''
            make_link: false
            path: ''
            absolute: false
            external: false
            replace_spaces: false
            path_case: none
            trim_whitespace: false
            alt: ''
            rel: ''
            link_class: ''
            prefix: ''
            suffix: ''
            target: ''
            nl2br: false
            max_length: 0
            word_boundary: true
            ellipsis: true
            more_link: false
            more_link_text: ''
            more_link_path: ''
            strip_tags: false
            trim: false
            preserve_tags: ''
            html: false
          element_type: ''
          element_class: ''
          element_label_type: ''
          element_label_class: ''
          element_label_colon: true
          element_wrapper_type: ''
          element_wrapper_class: ''
          element_default_classes: true
          empty: ''
          hide_empty: false
          empty_zero: false
          hide_alter_empty: true
          entity_type: node
          entity_field: changed
      arguments:
        title:
          id: title
          table: node_field_data
          field: title
          default_action: default
          exception:
            title_enable: true
          default_argument_type: fixed
          default_argument_options:
            argument: a
          summary:
            format: default_summary
          specify_validation: true
          glossary: true
          limit: 1
          case: upper
          path_case: lower
          transform_dash: false
          plugin_id: string
          relationship: none
          group_type: group
          admin_label: ''
          title_enable: false
          title: ''
          default_argument_skip_url: false
          summary_options: {  }
          validate:
            type: none
            fail: 'not found'
          validate_options: {  }
          break_phrase: false
          entity_type: node
          entity_field: title
      relationships:
        uid:
          id: uid
          table: node_field_data
          field: uid
          plugin_id: standard
          relationship: none
          group_type: group
          admin_label: author
          required: false
      style:
        type: table
        options:
          columns:
            title: title
            name: name
            changed: changed
          default: title
          info:
            title:
              sortable: true
              separator: ''
            name:
              sortable: true
              separator: ''
            changed:
              sortable: true
              separator: ''
          override: true
          sticky: false
          grouping: {  }
          row_class: ''
          default_row_class: true
          uses_fields: false
          order: asc
          summary: ''
          empty_table: false
      row:
        type: fields
        options:
          inline: {  }
          separator: ''
          hide_empty: false
          default_field_elements: true
      header: {  }
      footer: {  }
      empty: {  }
      sorts: {  }
      filters:
        langcode:
          id: langcode
          table: node_field_data
          field: langcode
          relationship: none
          group_type: group
          admin_label: ''
          operator: in
          value:
            '***LANGUAGE_language_content***': '***LANGUAGE_language_content***'
          group: 1
          exposed: false
          expose:
            operator_id: ''
            label: ''
            description: ''
            use_operator: false
            operator: ''
            identifier: ''
            required: false
            remember: false
            multiple: false
            remember_roles:
              authenticated: authenticated
            reduce: false
          is_grouped: false
          group_info:
            label: ''
            description: ''
            identifier: ''
            optional: true
            widget: select
            multiple: false
            remember: false
            default_group: All
            default_group_multiple: {  }
            group_items: {  }
          plugin_id: language
          entity_type: node
          entity_field: langcode
      display_extenders: {  }
    cache_metadata:
      contexts:
        - 'languages:language_content'
        - 'languages:language_interface'
        - url
        - url.query_args
        - 'user.node_grants:view'
        - user.permissions
      max-age: 0
      tags: {  }
  attachment_1:
    id: attachment_1
    display_title: 添付
    display_plugin: attachment
    position: 2
    display_options:
      query:
        type: views_query
        options: {  }
      pager:
        type: none
        options:
          offset: 0
          items_per_page: 0
      defaults:
        arguments: false
      arguments:
        title:
          id: title
          table: node_field_data
          field: title
          default_action: summary
          exception:
            title_enable: true
          default_argument_type: fixed
          default_argument_options:
            argument: a
          summary:
            format: unformatted_summary
          summary_options:
            items_per_page: 25
            inline: true
            separator: ' | '
          specify_validation: true
          glossary: true
          limit: 1
          case: upper
          path_case: lower
          transform_dash: false
          plugin_id: string
          relationship: none
          group_type: group
          admin_label: ''
          title_enable: false
          title: ''
          default_argument_skip_url: false
          validate:
            type: none
            fail: 'not found'
          validate_options: {  }
          break_phrase: false
          entity_type: node
          entity_field: title
      displays:
        default: default
        page_1: page_1
      inherit_arguments: false
      display_extenders: {  }
    cache_metadata:
      contexts:
        - 'languages:language_content'
        - 'languages:language_interface'
        - url
        - url.query_args
        - 'user.node_grants:view'
        - user.permissions
      max-age: 0
      tags: {  }
  page_1:
    id: page_1
    display_title: Page
    display_plugin: page
    position: 1
    display_options:
      query:
        type: views_query
        options: {  }
      path: glossary
      menu:
        type: normal
        title: Glossary
        weight: 0
        menu_name: main
        parent: ''
      display_extenders: {  }
    cache_metadata:
      contexts:
        - 'languages:language_content'
        - 'languages:language_interface'
        - url
        - url.query_args
        - 'user.node_grants:view'
        - user.permissions
      max-age: 0
      tags: {  }