So great, this is one of the most useful books I've ever read. I'm quite good with Excel but I still picked up some great tricks and methodologies here. Also there were many tips that I knew, but had only found out for myself within the last year or so. I would recommend this to all skill levels.
Despite having read that there is "retread" and the fact that it has a co-author I'm moving straight on to his much longer "dashboard" book