Oh, it's not that altruistic; if it's a good Haskell book, then it's probably worth it. The smidgen of altruism is buying it instead of just reading the PDF.

I'll probably read a bunch of the PDF first to find out, though. It's not what you'd ordinarily expect a Haskell text to be; it's a text on mathematical reasoning, using Haskell as a tool. As such, it may not get into Haskell's hard parts. (I have a very basic grasp of monads, but I'm just barely aware of the existence of arrows.)