Just wanted to add, as someone who bought that book linked above, it is not going to help you much because it is referring to the 2.0 version of IPB. Most of the things it covers are basic and it doesn't go into that much detail on all the things IPB can do. I did learn the admin interface with it, but if you never worked with 2.0 and are starting IPB with 3.0, I would not bother getting that book.
I do think that when I was a first time user, I did have trouble finding the documentation for the products, but that wasn't because it wasn't provided, it was just newbie-ness. This was back when there were two sites, ipsbeyond (I think it was) and the company site, which added to my confusion. In its current status, it seems to be very easy to find the information. I hadn't checked the new knowledge base until I saw this article...I just learned a couple of things I had questions about :D