An FYI about ereader formats --
As long as a book does not have DRM
(Digital Rights Management) attached to it, you can legally convert many books into a format your ereader can display if it is for personal use only
. DMCA (Digital Millennium Copyright Act) makes removing DRM from ebooks illegal in the US, but the U.S. Copyright Office does allow for some exemptions
|4. Literary works distributed in ebook format when all existing ebook editions of the work (including digital text editions made available by authorized entities) contain access controls that prevent the enabling either of the book’s read-aloud function or of screen readers that render the text into a specialized format.
Definitely read more there so you can stay legal.
Most to all Library ebooks have DRM attached in order to be able to keep checkout times to no more than 2 weeks.
That said -- Calibre
is a free download that I use to convert many file types. Since my Kindle can read native PDFs now, that tends to be the format I convert to most. It's been really helpful since some books I previously owned were in different formats and some new ones are only available in formats my Kindle can't read or convert.