The book assumes that you are up to university first-year standards in mathematics and physics. It then divides the subject into nine topics. We start by defining the term 'planet', and then considering the form of the solar energy source. Chapters three and four consider orbits and the restricted three-body problem. We then have a detailed discussion of extrasolar planets. Chapters six, seven, and eight review planetary interiors, surfaces, and atmospheres. The book ends with a comprehensive chapter on planetary formation. The text abounds with terms like geostrophic balance, Hadley circulation, Jeans' mass, oligarchic growth, Toomre stability criterion, planetary migration, tidal circularization, hot Jupiters, and mean-motion resonances. I recommend it most strongly. It is spot on. I did however have one little caveat. It skates over the mysteries. It gives the impression that our understanding is nearly complete. I always liked to tease my students with a few left-field questions. Was Mercury once a satellite of Venus? Why does Venus spin so slowly? Why has Earth only one moon? Why do Jupiter and Saturn go round every ten hours? Why has Uranus been tipped over? Why does the system end at Neptune? How many comets are left? Does every planetary system have an asteroid belt? Why have we only got eight planets? How does planetary origin depend on stellar mass and singularity? And so on. At least it gives them the impression that there is still plenty of work to do.

David W. Hughes. 2021 October The Observatory