Just make sure you've done your research and determined how much the book is at your local bookstore. A coworker almost bought a book from Amazon until she caught herself. She realized that, with the shipping, it was going to end up being twice what she could get it for in the store. Amazon is good, but their shipping and handling can be expensive - depending on what you're buying. Just make sure you're aware of that and are taking it into account.
Also, make sure you keep a record of when you placed the order, how long it's supposed to take to ship, etc. There have been some people not happy with Amazon. Overall, they're good, but they do have their glitches like any other company. They don't always keep you updated on the status. You need to make sure you stay on top of things and receive it when you expect it.