The Hiarcs 13 Pro book is a very strong and varied opening book derived from top correspondence and over the board human games together with the best computer games giving a superb combination with the latest cutting edge chess theory and a wealth of novelties to provide a huge repertoire of finely tuned variations. In addition to this strong basis the book has many novelties and variations that have been analysed by HIARCS to eliminate mistakes and improve the quality of book. The book is right up to date as of mid December 2010 including even games from the London Chess Classic and Moscow tournaments. With 2,925,276 positions, 382,899 variations and statistics from 678,641 high quality games the Hiarcs13 Pro book is a great resource for the active player who wants to be right up to date. The Hiarcs 13 Pro book has a very large amount of playable variations which gives a lot of variety and means the book is able to address the needs of many different players, from human tournament preparation to online computer games. Despite having more variety than most other commercial books the Hiarcs 13 Pro Book is significantly stronger typically scoring 55+% in head to head matches between books with equal engines over 300 games. For example, in a match of 300 games against the highly rated Rybka 4 book, the Hiarcs 13 Pro book scored more than 55%. Hiarcs 13 customers who already have the Hiarcs 13 Lite opening book will be delighted to know the Pro book adds up to 50 Elo to the strength of the program. The book is written by Mark Uniacke, the author of HIARCS, and he has been supported by Correspondence IM Harvey, Williamson and computer chess expert Eric Hallsworth, both of whom are also part of Team HIARCS. The HIARCS 13 Pro openings book can be used on it\'s own, with HIARCS 13 and your other favourite engines in any Chessbase graphical user interface.