Google has a book store which I’ve recently found. While I normally use Amazon, Google Books might be a good alternative. I don’t see anything which says Free Shipping so make sure you compare all the costs before ordering. I did check and the Excel 2010 book which costs $16.99 on Google, costs $16.49 with Free shipping on Amazon if you have the $25 minimum. Caveat Emptor.
One of the great features on Google books is that they have a number of FREE books which you can download as pdf files. These are mainly older books, but there are still some great classics available for Free.