Operating system: Mac OS X, Windows 7, Windows Vista, Linux, Windows XP.
Supported input formats: CBZ, CBR, CBC, CHM, EPUB, FB2, HTML, LIT, LRF, MOBI, ODT, PDF, PRC, PDB, PML, RB, RTF, TCR, TXT, DJVU, HTMLZ, SNB, TXTZ, DOCX, AZW4, AZW3, AZW.
Supported output formats: EPUB, FB2, OEB, LIT, LRF, MOBI, PDB, PMLZ, RB, PDF, TCR, TXT, HTMLZ, RTF, SNB, TXTZ, DOCX, AZW3.
Calibre is a free and open source e-book library management application developed by users of e-books for users of e-books. It can convert from a huge number of formats to a huge number of formats.
The conversion engine has lots of powerful features. It allow rescale all font sizes, ensuring the output e-book is readable no matter what font sizes the input document uses. It can automatically detect/create book structure, like chapters and Table of Contents. Also, it can insert the book metadata into a "Book Jacket" at the start of the book.
Calibre has a built-in ebook viewer that can display all the major ebook formats. It has full support for Table of Contents, bookmarks, CSS, a reference mode, printing, searching, copying, customizing the rendering via a user style sheet, embedded fonts, etc.
Tip: To convert to KF8 set the output format in the calibre conversion dialog to AZW3.