When it comes to converting eBooks from one format to another, you have likely heard of Calibre. It remains one of the most popular tools out there, and is deeply expansive. In the past, they have catered exclusively to users, but now that Sigil is not actively developed anymore, they are trying to appeal towards creators.
Calibre 2.0 is now available and the eBook Creator package that debuted last year has undergone a severe revisement. One of the most compelling is the spell check system, which now allows for the manual importing of dictionaries. It also has newfound support to extrapolate PDF metadata and the ability to click on any HTML/OPF/NCX tag name or CSS property and the editor will open some help for that item in your browser.
Many users are attracted to Calibre for a number of reasons. Some want to simply make eBooks out of popular websites, and read them on their ereader or tablet. Others download 3rd party plugins to strip the DRM off of purchased content.
Calibre has a very clunky and unintuitive interface and may alienate the average user. It has very extensive options to edit meta data or to optimize an eBook for a specific device, such as a Kindle, Kobo or Nook. It is a little known tool in the hardcore e-reading world, but lead developer Kovid Goyle hopes that indie authors and small publishing companies will take a second look at it.