This is an original GM parts book for 82 - 92 F body Pontiacs.
The book has engine and transmission decoding info, parts illustrations and data section, numerical listing (handy for referencing if you are looking on ebay at a GM part number that might be correct for you), tons of info. It includes the 89 Turbo Trans Am if you happen to be fortunate enough to own one of them!
Anyway, it's in a binder, but not an original GM parts binder, and it has a few loose pages although from what I can see, all the pages are there except the front cover.
Thus the price, $20 plus actual shipping costs. I couldn't even find one listed on ebay, or in the sold section there, so clearly it must not be an easy book to find.