For those who wish to purchase the text, Art History Second Edition by Marilyn Stokstad, I recommend the two volume, hardback, slip covered edition. The price is about $95.00; however the two paperback, school text volumes are $72.50 apiece. Remember, there is NO requirement to purchase the text.
There is also a huge one volume hardback edition for about $65.00. It's a backbreaker to carry but less expensive.

There are also used versions available, some at good prices. 

These texts may be found at any of the major on-line book stores. Here is a link to the boxed set at Amazon.com.
Art History  by Marilyn Stokstad-Two volume boxed set.

And to the backbreaking edition.  
Art History by Marilyn Stokstad--One volume hardback.

 I highly recommend having a copy of a book called  The Annotated Mona Lisa. Students say this is the most useful review tool available for the AP Art History test.. She also has a book entitled The Annotated Arch about architecture. I think it's good, but I haven't really used it that much. 

Here is a link to the title at Amazon.com. You can choose either new or used, all at a good price.. 
Annotated Mona Lisa