I have redesigned my small Arena Mainbook, generated from human master games of 2600+ Elo. The new 2600_24.abk has a book depth of 24 plies now, 89.512 moves. The database contained 8.137 games, no short draws, only relatively short wins. This untuned book is mainly recommendable for "book neutral" matches and tournaments, where all engines use the same. Due to GM practise, there are holes in seldom variants (i.e. after 1.Nc3 or in Pirc). OTOH, it should provide a fairly good theory support in many of the most usual opening variants, up to the 10th to 12th move.
http://members.aon.at/computerschach/Arenabook2600a.zip (432 KB zipped)
To use at your own risk!
