Nate, it's really annoying to come on and see a post deleted by you because of spoilers
Now I wanna know what you know that we mere mortals don't!
The Artbook did give us new information about the next chapter in the quintology, but at the time that was Stranger, and now we know lots more about him.
The real interest for me (other than the 'purdy pictures') is the stuff it told us that should have been in 'Munch' and wasn't, like stuff about Maggie and Sam (though there's precious little of even that, it must be said). It does give you a sense of how incomplete Munch really was when it was released, and how that sort of crippled the series for Abe. It's section on Munch's Oddysee has loads of concepts and ideas thirsting for further development.