I got a cool Cayenne Book at Ebay - its really one of the best automotive books I ever readed. Not the typical marketing blabla nor important tech data missing. The technical parts and history of the V8 Cayennes are very detailled in text, drawings and pics.

I think you can also get a english version of it on this site:

It`s the ATZ/MTZ Cayenne Extra Brochure wich been released July 2003 - you don`t find it on this website but there is a contact where you can order it.

They have also some other cool titles.