Its focus is on games and puzzles that have seen real-world play, rather than ones that have been invented for a purely mathematical purpose.

[2] In this area it is common for puzzles and games such as sudoku, Rush Hour, reversi, and chess (in generalized forms with arbitrarily large boards) to be computationally difficult: sudoku is NP-complete, Rush Hour and reversi are PSPACE-complete, and chess is EXPTIME-complete.

Beyond proving new results along these lines, the book aims to provide a unifying framework for proving such results, through the use of nondeterministic constraint logic, an abstract combinatorial problem that more closely resembles game play than the more classical problems previously used for completeness proofs.

An appendix provides a review of the methods from computational complexity theory needed in this study, for readers unfamiliar with this area.

[4] Leon Harkleroad is somewhat more critical, writing that the book feels padded in places,[3] and Joseph O'Rourke complains that its organization, with many pages of abstract mathematics before reaching the real-world games, does not lend itself to cover-to-cover reading.