National Master Dan Heisman has been teaching chess for some forty years, and in his writings he often references the work of Dr. Adriaan de Groot, who did pioneering chess research in the 1930s. Dr. de Groot worked with players with a range of playing strength, including the top players of the day. He would present players with an interesting position, but not a "White to move and win" kind of position. The player was asked to find a move while verbalizing everything he was thinking. This allowed de Groot to compare the thought processes of world-class players with lesser, but still strong, players.
The Improving Chess Thinker is a compilation of some of the work Heisman has done with hundreds of chess friends and students, duplicating the approach of de Groot. Heisman has been using de Groot and similar positions since his teenage years, so he has quite a database to work with. In fact, he suggests that he has probably used the de Groot test more than de Groot himself.
In this book, Heisman also takes from the approach of IM Jeremy Silman in his highly regarded Silman's Complete Endgame Course. Silman doesn't break down his endgame instruction by theme, as in most endgame manuals. Instead, he organizes his material by player rating, providing the reader with rating-appropriate material in a step-by-step manner.
The full review can be seen at the ChessCafe primary book review page for the next week.