I've found the book selection on iBookstore to be pretty limited thus far.
I had a list of about 10 books I'd hoped to buy, books that were all available for Kindle, and only 3 of them were available on iBookstore. Doh!
Okay but can we give Apple just a little bit of slack... Amazons ebook store has been around for quite some time and the iBook Store what? 8 hours or so? Somehow I think the selections will fill up quite quickly if the press and initial user experiences are any indication. Publishers not on the store will be crying to get in once worldwide sales ramp up **and** international iBook Store negotiations start getting finalized (not an easy feat mind you - this could take some time and lots of people aren't gonna wanna hear it but remember iTunes Music didn't go international overnight either).