How to trim body text (field_body)?
There's a few solutions you can try but take note truncating strings with html is generally a bad idea due to having potential unclosed or malformed tags.

1. Use |raw to output the html as html, may produce malformed tags:

{% set text = content.field_body|render %}
{{ text|length &gt; 200 ? text|slice(0, 200)|raw ~ '...' : text|raw }}


2. Strip html first, cleaner:

{% set text = content.field_body|render|striptags %}
{{ text|length &gt; 200 ? text|slice(0, 200) ~ '...' : text }}


3. Register a twig extension (untested):

https://gist.github.com/leon/2857883

Another helpful extension you can check out is the Text extension, which helps you prevent chopping up words:

http://twig.sensiolabs.org/doc/extensions/text.html