Seconding this! It's one of the very few tech books I've read cover to cover more than once. I similarly find myself revisiting individual pieces of it often.

It completely changed the way I thought about the role of type systems -- and I don't even mean in terms of monads, functors, or any other higher level category theoretic stuff. I mean just the day-to-day business coding idea of representing more of your domain directly in the type system.

I now find that pencil and paper is the best programming tool. It's massively easier to iterate on types and arrows between them than it is to pluck away against and refactor actual implementations.