Part of Oxford University Press' The Facts series, Baron-Cohen is a very well known researcher and author (and advocate) for autism spectrum. He prefers to call it "autism spectrum condition" vs "autism spectrum disorder", because he believes that while some aspects are clearly dis-abilities, other aspects are "talents". It's really one of his most charming traits.
Baron-Cohen had previously written a similar, short overview of autism and treated this book as an opportunity to bring that work up to date with developments. Chapter 5, "The Psychology of autism and Asperger syndrome" illustrates well the central weakness of this work (and, arguably, Baron-Cohen's least charming trait as a writer): he presents "five major psychological theories of autism and Asperger syndrome" with attributing these theories to any person or group of persons or clinics or research entities or whatever. Since Baron-Cohen is, IIRC, the creator and prime advocate of one of these theories, and since that theory gets quite a lot more space devoted to it in the text, acknowledging that he had a horse in this race would have been nice. This is the most clear example of Baron-Cohen using a general overview to plug his own ideas, but it is by no means the only one.
Fortunately, I dislike Baron-Cohen's theories about spectrum less than I dislike other people's theories about autism, so while I disapprove of the behavior, I don't disapprove of the result. It's a useful that said, there are some additional, non-trivial issues. First, Baron-Cohen presents PDD-NOS as a fewer-traits version of autism (it's the way I think of it, too), but again, other people treat it differently. Second, I don't think Baron-Cohen really "gets" where stereotypies, perseveration, repetition, the need for sameness actually comes from. He treats it as a cognitive activity (part of his systematizing behavior). I find repetition restful and pleasurable, and distinctly NOT cognitive. And I don't think I'm alone.
Baron-Cohen, Simon, _Autism and Asperger Syndrome_. New York: Oxford University Press, 2008.
In any event, if you are looking for a short, "safe", introduction to spectrum, I have not seen better in book form.