iBooks just received an update that adds dictionary look-up of words as well as quick, closer views of in-line images, and updated PDF controls for quicker browsing. Generally, it adds a number of features missing both from iBooks and the iPad Kindle app.
Generally, I like the new features. I really missed the standalone Kindle’s in-built dictionary and being able to view images in full size – as well as embedded audio and video in some books – is a big improvement. The update is free and available now.