Generally a Korean book translated as "Essential Formulas" or "Standard Formulas" is a joseki book. This one poses 50 "problems" for the purpose of discussing the corner positions. The key answer diagrams are headed by didactic percentages to support the theory that it is a problem book, however, it is more fashionable than something else to compose a listing of variants in a problem and answer format.
The contents is more interesting. The author wants to teach joseki without forcing the reader to read a dictionary. So far he succeeds. However, a problem / answer style is also rather dry. On the other hand, the 0/30/50/100/120 percentages support another intention: Per position about four moves one might likely consider are assigned these rough qualifying numbers. Thereby the reader is left with little to ask - he gets the intersections to be considered and their evalution but the complex variations are omitted. The selected positions are from popular joseki and ask for their development just before their intermediate difficulties occur. So the book covers some of the most frequent practical joseki problems in a way that also teaches to think about tactics similarly in other joseki. A small number of variations is particularly noteworthy because they are new or show good sacrifices.
Among the books concentrating on the method of teaching by examples Essential Formulas is about the best one might get. So if you like to study joseki in exactly this way, read this book first. However, do not expect to avoid your dictionary as soon as you face other non-trivial joseki.
Date: 26 Nov 2001