Drugs like Tymlos that work by building new bone. Bisphosphonates work by stopping old bone from being reabsorbed, so, yes, your bone density will increase, but the question is how good is the bone that's there? So bone builders work on the osteoblast part of the equation while anti-resorptives (bisphosphnates) work on osteoclasts. The book helps to explain the mechanisms by which the different drugs work. It's really worth the read. You will understand so much more about how your body is working and what's gone off kilter if you read it. Generally speaking, the bone builder drugs are considered to be more heavy duty and they certainly are more expensive, so, yes, side effects can be more of an issue. Having said that, many people have such bad reactions to bisphosphonates that they can't take them and have to go to the bone builders at which point the insurance will pay for them.