The strapline for the book says 'a realistic introduction...' and that's exactly what you get.
As a newcomer to BDSM, I was looking for something to give me an introduction to the scene. I had visited several websites' discussion pages, but found the things there a bit cliquey and not very helpful.
SM101, on the other hand, was extremely useful. The book assumes no prior knowledge of S & M, but takes the reader through the principles of playing, how to play safely, use of safewords and contracts. It then goes on to look at some of the techniques used, such as whipping, ropework, blindfolds and gags, and tells you how to improvise some equipment yourself. It has lots of ideas for scenes, and also tells you how to find like-minded people in your area.
The writing style is relaxed, honest and friendly, and throughout the book there are amusing quotes from people in the BDSM community, which help give it a down to earth quality - it's not at all voyeuristic or pervy - although I'm not sure I'd leave it on the coffee table!
The only drawback is that, with it being an American book, many of the contacts and suppliers are unavailable here - though there are of course web addresses and links too.
All in all, an extremely good introduction to the BDSM lifestlye. I found it a real confidence boost... and it gave me several ideas to try!