This book is by the world's leading authors. It is written by doctors, for doctors. I am not a medical doctor (my PhD is in economics) so some of it went over my head. But I got a lot from the bits I did understand, and was able to discuss the treatment options with my doctor more effectively as a result.
It is well organised - the lay reader can pretty much turn to section 10 "Therapy" immediately, and discover the options, the pros and cons, and so on. It won't be the easiest 130 pages you'll ever read, but I found it useful. The final chapter, on future therapies, gives you a sense of what might be around the corner, which is useful if, like me, you are 40.
Other chapters are much more specialised - for example, the chapter covering the connection between organ transplants and osteoporosis is important if you have an organ transplant, but of limited interest to the general reader.
Although I like this book, and am glad to have it on my shelf, I would recommend Orwell / Atlas of osteoporosis as a starting point in preference to this book. It is easier, and shorter.