I read HSoE a couple of weeks ago to see what more adacamically oriented Haskell books were like. I'm glad I started with RWH, and LYaH covers a lot more ground, but HSoE is excellent in the clarity of what it does cover, in using graphics quite nicely for examples (dated graphics library though), and especially for teaching how to do proofs using Haskell (which also includes teaching well how to evaluate haskell code in your head, and how to think about space leaks).

If the new book does the same, and also teaches something about computer music, it sounds like a real winner.