In order to see what version of FBReader you're running, you should open a book with FBReader and go to "settings" and click "About book".
The newest FBReader hack is located in its sticky:
https://www.mobileread.com/forums/showthread.php?t=65865
It's quite normal that AdobeViewer-opened books look better, since Adobe Viewer doesn't ignore the CSS codes inside of the file. However, people value more the customization capabilities of FBReader.