I have been thinking about whether or not the reason that there haven't been any significant improvements in the IBooks store site in terms of improving the browsing capabilities is that the IBooks feature is just one of thousands of aps and functions available on the IPad. The Kindle on the other hand, not only is a dedicated ereader-therefore Amazon would naturally concentrate on making it as useful as possible, but it mimics the browsing system of the Amazon bookstore-which has years of programing behind it.
I just hope that soon the people at Apple will devote a little more time and money making IBooks store a more welcoming environment. Once you get a book, the experience is wonderful, but for now it feels more like the book department of WalMart than a high-end book store (which is what I expected from Apple).