There is a new version 'a' which reacts to a smaller tilt angle:
http://pbook.s3.amazonaws.com/fbreader_180b.zip
Please copy to directory /system/bin on the PocketBook.
Updated sources (just the changed files):
http://pbook.s3.amazonaws.com/fbreader_180b_src.zip
P.S. Links Updated to better 'b' version.