# Are there any moves in the opening stage that are perfectly sound but not book moves?

In the opening stage, are there any moves that are perfectly sound but are not book moves? Here a book move, is defined in Wikipedia as follows:

Opening moves that are considered standard (often catalogued in a reference work such as the Encyclopaedia of Chess Openings) are referred to as "book moves", or simply "book". Reference works often present move sequences in simple algebraic notation, opening trees, or theory tables.

By a sound move, I mean a move that is completely reasonable in a certain opening position and does not create any weaknesses. (There may be a better definition, but you probably know what I mean.)

• Have a look at the irregular openings: Depending the opening book you choose as a frame of reference for what is recognized as regular, you might find those mentioned on the linked page as good candidates for what you're looking for, e.g. `1.b3`. Commented Dec 10, 2019 at 16:53
• If both sides make lesser popular moves (though sound), they can be out of the book very quickly. For example, `1.d4 d5 2.Nf3 Bg4 3.g3 e6 4.Ne5`, `4.Ne5` is not in lichess master game database. Commented Dec 10, 2019 at 18:51
• 'Book' is an arbitrary definition. There are definitely enough sound moves for not all of them to be labeled 'book'. Commented Dec 10, 2019 at 19:54

Obviously, you are not the first chess player to think about alternatives to the 'book moves'.

I think it is a solid assumption that all possible moves that deviate from the book move have been considered by someone already, and probably by someone with some playing strength.
So either those moves are good enough (equivalent) to 'book moves' and therefore they would have made it in the books by now, or they are (considered) at least slightly inferior.

If you consider playing an inferior move, you will have to balance the expected 'loss' from the inferiority against the potential 'gain' from forcing your opponent into a non-book variant (which you have analyzed in depth before, and he probably didn't). Depending on his strength in 'book openings' compared to his strength in 'think-yourself', this might be a good deal for you or not.

Note that this is not an uncommon idea - nearly all chess players I know have taken this approach from time to time, and more or less successful. Try it, but don't expect your opponent to be shocked out of his mind.

No, not because there are not things that are not sound, but virtually every early divergence, if at all good, has been played...and virtually every bad divergence.

• A century ago, players said that chess was dead and the openings were completely solved, then came the hypermodernists. This trend continued until, at least, 2000. Just when chess became stale again, Leela show that you can play the obviously bad 1.a4. Commented Dec 11, 2019 at 2:22
• There is a big difference between chess being dead, and virtually all reasonable moves in the very opening having been tried. I am also not talking about some novelty on move 27, just the first 5-10 moves. Try looking at the openings in ChessBase...9 million games covers a lot of early moves. Commented Dec 11, 2019 at 2:33
• The example I gave was on move one. The point is that that move was considered bad and now is considered good. Your entire counterpoint is invalid just as the changing opening theory. Commented Dec 11, 2019 at 6:40

Depends what you mean by sound. And what book you think is the authority.

Could a computer beat that move? Maybe.

Would a person beat it? Much less likely.

There are many playable moves that are not in the book. I found an absolutely sound one that is not in the book and always gives some advantage. I also found an excellent one for time limited OTB play that gives a good winning percentage.

Eventually every good move will be played and should end up in the book.