The new iBooks 1.5 is out. It's great. It has a nighttime mode to make reading books in the dark easier on the eyes and full-screen layout with none of the stupidly gimmicky backdrop. Just beautiful typography. More useful features:
• New typefaces, including Athelas, Charter, Iowan and Seravek. Some are great.
• Redesigned annotation palette makes it easier to choose a color for your highlighted text.
• Redesigned classic covers for public domain books (these are good, although I always make my own by looking for first edition covers).
I've been using it for a bit now and it's really nice. Go and upgrade now!