Rybka 4 Aquarium Opening Book provides latest chess theory approved on millions of advanced chess games and matches of top human players. It includes over 18,000,000 positions.

Rybka 4 Aquarium Opening Book is a thoroughly researched and up to date collection of modern opening lines. It can be used as an opening book in chess engine matches, an opening guide in correspondence chess, as well as a source for general opening studies and tournament preparation by players at all levels.

The author of the book, Jiri Dufek, is one of Veselin Topalov's seconds in his world championship match against Viswanathan Anand (Sofia 2010). He is one of the top freestyle players in the world, and an International Master of correspondence chess.

The opening book is based on a careful selection of the most important theoretical games, both by human players and chess engines. All variations were carefully reviewed and moves were classified and color coded with green color (recommended moves), red (not recommended), blue (recommended for human tournaments but not computer tournaments) and black (neutral moves). If you want to build a successful opening repertoire, based on active but solid lines, this is the opening book for you!

As a special bonus from ChessOK, the book includes chess trees (positional databases) containing computer evaluations of the moves in the book and statistics showing their popularity in human games and in correspondence play. The trees also show changes to the popularity of moves in the past year.

The book is specially designed to use all the advantages of navigation in multi-column tree view of Rybka Aquarium GUI.