There isn't any other book I'm aware of that gives the coordinates of ALL the regular polytopes in 4 dimensions. (Higher dimensions, also covered, don't have as many) He even includes the 'biggie' which is the 120-cell (or the 600-cell, depending on how you look at it). And of course Sommerville also gives the coordinates of the dodecahedron (a building block of the 120-cell) and the icosahedron, platonic 3D solids. If you want to start to party down in 4D with more than just the classic hypercube, trust me, this book is one to get.

I was just comparing this book to the newer Coxeter "Regular polytopes":Regular Polytopes. My original $1.50 copy published in 1958 is falling apart and is marginal noted for end to end.
They want $50 for a used version of this book!
Reminds me of the other Coxeter Polytope book that they want $125 for!
This book may be the key to understanding Coxeter.