The first publication of the orbifold notation by its inventor About 10 pages. A standard reference. It contains discussions and Cayley diagrams for the 17 wallpaper groups. A standard reference. The book is mostly focused on polytopes.
Several sections give a brief but significant discussion on symmetry groups.
The math here is rigorous, but is lively written and accessible to undergraduate. Half of the book comprise well-done illustrations. For example, in this book you'll find a database of tilings and patterns by various classifications schemes, all illustrated. This is a standard reference on the topic, and no other book approaches its scope or depth. This will probably remain so a few years after 2000.