From my experience with Chessmaster, Extreme Chess,
Different databases have different "books".
Yeah, true
But what I'm currently wondering right now is why Chess.com is removing book moves. It used to be a book move but now it isn't.
Noticed the same for the Kholmov Gambit which I play a lot, but even the first few moves (classed as Petrov's Defence) aren't book moves anymore.
Of course all the previous sequences mentioned in this thread are not listed in https://www.chess.com/awards/<user_name>/books, but there does seem some kind of change lately.
We have completely overhauled our book move database to align it with well-known opening theory. We've added known opening moves to the "book" classification and are removing moves that are bad. With this change, you'll get a more accurate sense of how well-versed you are in your favorite openings—and which openings you could study more.
https://www.chess.com/news/view/chesscom-launches-game-review-v2
That was posted in March.
In my last game, I played the Tennison Gambit against the Scandinavian (e4, d5, Nf3) every single time I had analysed this, it had been marked as a book move, as it is a book move. Its a well-known gambit with theory behind it.
Recently, I analysed a game where I played the Tennison Gambit, and my Nf3 was marked as a mistake!
Another example of this is the Fried Liver Attack. where Knight takes f7 is now a Brilliant Move.
I am extremely confused as to why this happens now. If it is a new change, It makes zero sense and I hate it.
You could never trust chess.c analysis or reviews. It's no different. However, they had ridiculous things like the Bongcloud down as book, whereas only a fool would consider it book.
We have completely overhauled our book move database to align it with well-known opening theory. We've added known opening moves to the "book" classification and are removing moves that are bad. With this change, you'll get a more accurate sense of how well-versed you are in your favorite openings—and which openings you could study more.
https://www.chess.com/news/view/chesscom-launches-game-review-v2
That was posted in March.
The bongcloud is still down as book so what you say seems inaccurate. That should be the very first to go.
the fools mate used to be book
the fools mate
there was some serious cleanup needed
game review changed amar opening from book to a mistake
:
That shows that this place is run by incompetents. Amar is not a mistake and is perfectly ok. Not very good but it's ridiculous to call it a mistake. I knew one guy on the congress circuit who played it all the time. It's an exceptionally solid and hard to beat method of playing the KIA.
In my last game, I played the Tennison Gambit against the Scandinavian (e4, d5, Nf3) every single time I had analysed this, it had been marked as a book move, as it is a book move. Its a well-known gambit with theory behind it.
Recently, I analysed a game where I played the Tennison Gambit, and my Nf3 was marked as a mistake!
Another example of this is the Fried Liver Attack. where Knight takes f7 is now a Brilliant Move.
I am extremely confused as to why this happens now. If it is a new change, It makes zero sense and I hate it.