FBReader is a great application that you can use as e-book reader in your Nokia N900, it supports several open e-book formats and automatically determines encoding. It is also able to automatically generate table of contents and hyphenation.

FBReader v0.10.7 supports the following file formats:
fb2, html, chm, plucker, palmdoc, ztxt, tcr (psion text), rtf, oeb, openreader, non-DRM’ed mobipocket, plain text and reads directly from tar, zip, gzip, bzip2 archives.

Download and Install