Im dont know if this has been mentioned in this thread already, or even how relevant it is to the posted question, but: have you read 'Grailpages: Original Comic Book Art And The Collectors' by Steven Payne ? It's mostly about the collectors and doesnt offer much in the way of advice and tips on collecting, but I enjoyed it just the same as it does manage to give you a warm and fuzzy feeling inside about being one of the people with this cool comic art collecting hobby.
http://www.amazon.com/gp/product/1605490156/
