My experience using crengine is full of trial and errors. The reader is very picky about "fb2.css" I had problems using css comments, newlines using pt or px in body etc.
Code:
body { text-align: justify; text-indent: 1em; font-family: "FreeSerif", serif; font-size: 12pt }
this didn't work
Code:
...
body { text-align: justify; text-indent: 1em; font-family: "FreeSerif", serif; font-size: 85% }
...
this works and is my current setting. You can get "FreeSerif" at
http://savannah.gnu.org/projects/freefont/