I went through the Pitt series first and picked up the Monk series with some trepidation...after twenty-odd books the Pitts were all beginning to look alike. I was pleasantly surprised by "The Face of a Stranger" and the Monk series remains one of my favorites.
Actually, it *is* possible to incur brain injury erasing memory but not touching your skills. We learned in class here at university about that, as they involve two separate areas of the brain. There are folks that can't remember yesterday but can still beautifully play the piano, perform surgery, etc.
True, some of Monk's amnesia is a bit selective, but this is a work of fiction and thus does entail inclusion of some possibly not-perfectly-realistic elements.
Monk's a great character, if not one easy to like. Flawed and all-too-human, it's also fun to watch his development through later books, so don't give up on him after "Face". Thomas Pitt was a *little* too perfect for my taste, so I rather like the darker character Monk presents. It's also a relief that Monk does not spontaneously recover his memory in a common author's cop-out. Also, Hester Latterly's the perfect foil for him, and their clashes are always amusing to read in each book, right from that first meeting in the countryside.
The mystery itself is interesting, and I noted that Ms. Perry once said that she intended for this to be a one-time book and not a series, intending to have Monk be the killer. I'm very glad she decided not to abandon him, even if he needs a good reality check at times. Not the absolute best of the Monk series, but a spirited and promising beginning to a great series.