I'm not a member of this community, so I'm going to throw this out as a suggestion and see how many votes it gets.

Consider linking to **isbn.nu**, which queries a number of online booksellers and shows prices for all of them. ([My current reading](http://isbn.nu/978-0-701-18390-5).) This is always my own choice these days, on Stack Exchange or elsewhere.

Be aware that [links to Amazon have the possibility of raising money for Stack Exchange](https://meta.stackexchange.com/questions/26964/auto-inserting-stack-overflow-affiliate-into-all-amazon-book-links). Whether you think that’s a point against them or a point in their favour is up to you.