I bought this book since it was recommended by the course instructor (the course was not a basic intro course, lecture 2 delved straight into monads, and lecture 3 was higher order monads.) I myself have some prior experience with Standard ML, and I don't feel like a stranger to functional programming in general. The result was that I ended up blowing through nearly half the book in one sitting (a few hours.)
While it does explain some of the syntactical oddities of Haskell I haven't seen elsewhere (guards, list comprehensions, etc), these are fairly simple things. Halfway through, he starts with a parser example (using monads), but since he doesn't really explain the why and how for the rather strained construction, I feel the point is somewhat lost. Sadly, monads aren't really delved into.
If you have any basic knowledge of functional programming (esp of the SML style), I'd recommend you move along to a move advanced book. But for the simple stuff, the author explains everything well.