One of the very first chapters is "Heap Profiling and Inspection," which is where too much laziness would manifest. So I really don't think this is fair.

We'll have to see when the book's done, but a practical, techniques-and-skills focused approach to Haskell optimization seems like it could be a really good resource. There are plenty of other tutorials out there ready to explain how `foldl` evaluates one more time.