Looking for a 3d math backup book.

I'm pretty well into this book
http://www.amazon.com/Primer-Graphic...3974953&sr=8-1

but am stuck on the quaternion operations (slepr, squad, exp, etc.) and the like and want a good book that backs it up in regards to making it a bit more understandable. I've seen these books

http://www.amazon.com/Mathematics-Pr...3974742&sr=8-2

http://www.amazon.com/Essential-Math...rdr_bb_product

and am wondering if anyone has suggestions.

I am postponing understanding them fully until later so I skipped the chapter, but want to have a good backup in-case I need a second opinion on another area.

Quaternions are not simple math. I think the first book does a good job of explaining them. Every other explanation I've seen is about ten times as difficult.

I understand the concept, but it's hard to visualize them like say Euler angles or even matrices. So when the book goes to doing he proofs for some of the calculation I get pretty lost. I'm no math wiz but I've gone through my rounds but still, I have some trouble.