"Encyclopedia of Gambits", consists of two main parts:
Part 1 (134 pages): a compilation of 80 (old) gambits by Matsukevich. Each gambit is introduced briefly (including the player or place it's named after) and explained in one or two annotated games (miniatures).
Part 2 (116 pages): Well-known trainer and GM Razuvaev shows and explains new gambit ideas in different openings. In 15 chapters these ideas are examined in detail, including the history of the idea and recent games. For example Razuvaev examines gambit ideas in the Scotch Opening, Mieses Variation and (of course) the recent g2-g4 ideas in the Slav (Shabalov-Shriov Attack).
In Russian Language but accessable also to non-Russian speakers.