apba baseball cards handbook

Can someone who either knows or is really passionate about apba baseball cards explain both this: http://www.ebay.com/itm/Handbook-for-APBA-Baseball-Cards-Edwin-Zack-1992-/350545817132?pt=LH_DefaultDomain_0&hash=item519e28ae2c, as well as why this book is so important?

I understand that this item had two bidders driving up the price, but really? Really?

Thanks, Mike

Edit: In case the link goes dead, the Zack, APBA Handbook, sold for $377. The seller is one of those drop off places.

I was given a huge hoard of apba stuff a few years ago and I tried to acquire this book...i believe it's out of print and hard to find...therefore expensive. It took me months to root through all of it and figure it out...book probably would have made it much easier!!!