Colel has been working the past months on several enhancements to the original Books.app and reached a point where it can be shared as a pre-release version with a wider audience. There are still a number of glitches, inconsistency in UI and lack of documentation. However the it's rather stable.
Features:
FB2 support, including support to zip-archived files;
Localization support, with English, Russian and draft German, Chinese and Japanese languages included;
Page scrolling with volume control buttons;
Auto-scroll with adjustable scrolling speed;
Increased book loading speed;
Table of contents for single-file books;
Book cover inside the text;
Opening files anywhere on the file system under /var - including both home dirs of users "root" and "mobile". Also /var/root/Downloads;
Color management for fore- and background in both day- and night-modes;
PDF, XLS and DOC viewer based on Safari engine;
Justified alignment and other small but very handy enhancements.