The book is aimed at beginners and the text is very dense, which saves a lot of time. The exercises were very useful to me and sometimes even enlightening. The one thing I found annoying was the lack of transparency in the sample code snippets: the code given in the book sometimes needs an import from the standard library to function, or it shadows a name from the standard library. All the problems can be solved by referencing the source files or hoogle but it's not as straightforward as it could be.
The book covers the basics fairly well but is very scarce on program complexity analysis, the type system, and monads.
If I had to recommend a "track" for learning haskell, it would go like this:
- Go through the haskell wikibook
- Read The Craft of Functional Programming up to chapter 18
- Read IO inside on the haskell wiki
- Read the rest of the book
- Find other more advanced resources...
All the while, there are exercises in the wikibook, in the book, on the haskell wiki at 99 problems, and at project euler.