<div class="display_selection wrap">
  view as
  <ul>
    <li class="<%= 'selected' unless params[:display] %>"><%= link_to "grid", books_path %></li>
    <li class="<%= 'selected' if params[:display] == :list %>"><%= link_to "list", book_list_path %></li>
  </ul>
</div>

<div class="display_selection wrap">
  view as
  <ul>
    <li class="<%= 'selected' unless params[:display] %>"><%= link_to "grid", books_path %></li>
    <li class="<%= 'selected' if params[:display] == 'list' %>"><%= link_to "list", book_list_path %></li>
  </ul>
</div>

Fix the check if list display is selected
Fix the check if list display is selected
