My wife and I have used this book (and prior editions) on several occasions when touring the UK. We have stayed in many of the places listed in the South West and in the South of England and also the Isle of Wight. I can tell you that this is a great resource and we've rarely had a problem either booking a place that was listed, or with the place itself once we got there. We've stayed in farms, castles, large country homes, houses perched on cliff tops, and lots of little places in between. The prices have always been great and compared to a regular chain hotel, low. We've been lucky in that the folks we've stayed with have been warm and accommodating and down right fun. We count several home owners now as friends. Yes, you will stay right in someones house and get to know their kids, their dogs and the owners themselves and you may well build friendships that you can count on when you go back for a visit. We've stayed at the same Cheshire farm house 3 times and know the whole family quite well; all because of this book.
It's unlikely that every single B+B listed is as excellent as the ones we've stayed in, but by and large, we've found this to be an excellent resource (even outdated versions still list active B+B's). Give it a shot if you are tired of the bland chain hotels.