This is the CTG that makes the rounds of the various chess forums. It is a very large opening book. About 11.5 GB. As a RAR file it’s still about 3.5 GB. It is a bad idea to try to use this in Fritz during an engine match or tournament, except maybe under very long time controls. It’s meant to be for correspondence players, and thus would be useful as a simple reference in either Fritz or ChessBase (or other software that can read a CTG). My understanding of correspondence chess is that engines are sometimes allowed, thus creating a need for an engine like CorChess. But for the most part they aren’t. And tablebases are sometimes allowed, but also, for the most part, verboten. The one thing they always allow for is an opening book. Thus the bigger the book, the more freedom you have to explore the moves the way you would with a chess engine. I realize that this is a bit of a dodgy approach to corr chess, but it’s not cheating, and it’s not disallowed.
https://www.mediafire.com/file/bl7hqnoc3mq500v/UpdateImmortal+2012a+final+v31-2.rar/file