All the books so far have the k-logs, and book 1 has the first part of the summer 09 updates at the back, but not the end. Book 0 hasn't appeared in print at all (yet? I'd buy it as a separate book). So there is an appreciable chunk of the text updates that don't appear in print. There are extras, as Cloudbreaker mentioned. Issue 1 of book 2 has some character concept art, and issue 2 has bios of all the Great Minds in the back, including some game world info we haven't gotten in the comic.
I know how it is to be broke, and Rob's chosen his own pay model knowing there'd be some who don't buy. But, still, its worth supporting when you're able. The Tool option's $33 and you get that much in store credit, so that's one way to save up for the books.