There are many theories out there that talk about how the planets formed and most people are content with knowing how it all got started. Mr. Dormand goes deeper into this question with his point of view. In his book he delves deep into theories about how the solar system was formed and what it should have evolved to with the current mass of the sun. The conclusions that he comes to is that the solar system did not have enough material to form all the existing planets. His theory is that we drifted through a dust cloud before the sun started shinning.
Many theories are looked at in extreme detail with formula's and conjecture. You walk from the earliest beginnings from the protodisk to what is left after 4.5 billion years. Many of the theories that Dorman goes over seem to have serious problems with certain aspects of the formation in several ways. All of which, except his turn out to be in error. Although Dormand pokes holes in the other theories, you learn a great deal as to how solar systems form and evolve.