Its nice and clean rich, good effort.
Only one suggestion that I could make that differrent :-
---- When you click 'add this book to the price comparison cart' - I'd have it automatically going to the cheapest merchant
either that or make the 'calculate best deal' button appear at the top. (that is unless you have it going to the highest commission bookstore by default and its part of the design)
Other than that it look excellent - you should do this for a living
