I found the exercises in this book to be very helpful. The photos and descriptions of the exercises are clear, and the exercises are easy to scale up in difficulty as you become stronger. With each exercise, you are told which specific muscles you will strengthen as well as which part of your skeleton (hips, spine, wrists, etc) that will be strengthened.
Without sacrificing effectiveness, the exercises are kept fairly simple, requiring minimal equipment. More than half of the exercises can be done with no equipment at all (enabling a very complete routine), and the remainder can be done with a little supplemental equipment, including a chair, step, theraband/dynaband, free-weights, wrist/ankle weights, and inflatible stability ball.
I'm in my mid-30s and relatively active. While I found I could *do* almost all the exercises in the book, there is definitely still room for me to improve. With the optional increases in difficulty built into each exercise, this book will keep me challenged for some time to come.
Having said that, many of the exercises are basic enough that someone who is experiencing compromised mobility or who is recovering from illness will be able to manage many of the exercises in the book.
This book motivated me to get off my duff and start reversing my loss in bone mass. I'd recommend this book for anyone who already has osteoporosis as well as for those who want to avoid it.