Bought this when thinking about a second pregnancy as I was very inactive during my first, and wanted some advice/hints about being more active when pregnant. It was perfect. I am not a full on runner, but it was just reassuring to read that women could still do exercise and there are many helpful tips and pieces of information about how to be active safely (not just running and not just for experienced runners).
I found that if you spoke to nearly anyone (dr, midwife, physio etc) they are very reluctant to recommend anything much at all apart from going for a walk - which I guess is fair enough as they would get the blame if something happened from other recommendations (even if it was completely random to have something bad happen).
This book has exercises, stretches and lots of info about walking/jogging/running and other exercises. I found it very helpful and reassuring. Obviously there are no guarantees, but it really isn't healthy to sit around doing nothing for the best part of a year when your body is under so much stress anyway - we need healthy forms of exercise to keep our bodies strong and flexible and fit enough for birth and new mummy duties.
Might not be for everyone, but I found it very good.