The apps page at WINE HQ has a good run down:
Reading a Secure ebook.
Reading a non-Secure ebook.
What does not
Importing new ebooks into the library (see below for how to add them manually).
Connecting to any online bookstore.
What was not tested
Importing/reading non-prc ebooks (books in something other than the mobipocket format).
I'd be curious to know how you go.