The AIA Official Guide to the 2007 AIA Contract Documents breaks down the individual sections of the Contracts and explains their proper use. While it is helpful to have a book that gathers all that information into one source, the AIA website also offers the same information for each contract under the “Instructions for Use” link. For example:
The link below leads you to the B101-2017 page.
Once on that page, selecting the “Instructions for Use” link from the list of resources will take you to this page.
Instructions for Use
Using the AIA Contract website in this way, I don’t think you need to buy the 2007 Contract Guide, especially because that book is now out of date.