I'll second that on David Pogue's "The Missing Manual" for Leopard. I'm reading it right now, actually. I've been away from Macs since Jaguar, and there have been MANY changes since then. This particular book has been getting me up to speed very quickly.
I find David's books informative, easy to read and comical in a geeky way. They're hella thick, so dig in if you plan on committing time to it.