A new edition of VW Camper - The Inside Story is out from Crowood and it looks awesome. I am ordering one this week. It's not cheap ($34) but it looks worth it and I have some others from this the author (David Eccles) and they are all great. Check out all the campers it covers:
Adventurwagen; Amescador; Arcomobil; Australian Campers; Auto-Sleeper; Bilbo's Campers; Campmobile; Canadiana; Canterbury Pitt; Caraversions Hitop; Danbury Conversions; Dehler Profi; Devon Conversions; Dormobile; Eurec Campers; EZ Campers; Gardena Gypsy; Holdsworth; Joch Camping; Kamper Kits; Karmann Coachbuilts; Moortown Motors; Oxley Coachcraft; Poba Campers; Reimo Conversions; Riviera/ASI Campers; Safare Custom Campers; Service Mota-Caravan; Slumberwagen; South African Campers; Sport Kocijan; Sportsmobile; Sundial Campers; Syro Kit Campers; T3 (T25) UK Campers; Tischer Demountables; Teca Conversions; Viking; Westfalia Campers and VW California.
To order, go to http://www.motorbooks.com/ and put "Eccles" in the search box.
I'll post some pictures from the book once I have had a chance to review it.