Book Moves

Why is it that book moves are important?

Assuming you mean openings, the book moves are the result of hundreds of years of study and they help prevent making a game deciding mistake in the first 5 moves.    Higher rated players, a mistake in the opening would be game over.  Low and mid rated players can "wing it" without knowing every single move.   The other thing is time... a 2500 rated play probably would not make a total goof up if they "winged it" but recreating the moves by thinking about each one costs time on the clock AND mental energy that could lead to mistakes an hour later (in a long game, of course).

They aren't.

I agree with the concept of opening lines. You can get a long way with simple development. I would think the plan behind the book (opening lines) moves are important. Develop with a plan (Silman)

That's a common misconception. Usually the difference between a "book move" and a move that's wrong according to theory is really, really small.

For instance after 1.e4 e5 2.Qf3 (oh no!), the position is probably equal.

The opening guidelines are important. 2.Qf3 seems to create problems. If not know moves later. It isnt a loser but 2.Nf3 is a better choice.

Which book do you mean? There are many written with different moves in them.

But that is a book opening.   It may not be the most popular choice but it has been studied and you can look up the responses to it, chances of white and black winning, variations after the queen move, and more. 

1.e4 e5 2.Qf3

The stronger the player the easier it will be to gain an advantage.

I agree.  The point isnt this silly opening, its that this opening and responses to it are in "the book".  The implication was, the queen move is not a book move, but it is -- it has a name, the responses to it are there to study, etc.  After reading up on it, the player can decide to do this or not -- that is the point of the book, which was the question at hand....

Professionals always stress the importance of there games on the opening and afterwards. Control of the center, getting an early advantage. (When wouldn't you want to be ahead and have control of the game.), Proper piece positioning. All start out of the opening.

Haven't you ever played a game that was completely different from proper openings and had pieces all in the wrong positions and King wide open ect. (Why they say bring major pieces out first. Pawn moves can't be put back. Ect.

Yes, for professionals. Because they and their opponents are already good at everything else, it makes sense for them to spend time improving the last few percent, and they are also good enough to make use of tiny advantages.

If you aren't good enough to make use of them yet, there are other things to learn that have way more effect on your game.

Of course I've played such games. Here's the start of my game from this weekend. Both players are rated 2000-ish.

Black was out of book after move 3, and white after 5. White was rated 2006, I was black and rated 1981.

As you can see, it was perfectly possible for me to reach a decent position without knowing any of the theory.

Not that it mattered, because then I chose a wrong plan and had some tactical oversights too, and after 30 moves white had a completely dominating position.

Not that that mattered, because then he thought he had a winning combination but there was a mistake in it, and I easily won the exchange up endgame.

Plenty to improve for both of us there, but most of the game had absolutely nothing to do with book moves, and if we had played 7 instead of 3 it would have mattered zilch.

This is absolutely typical below, say, 2300.

I disagree.   Knowing 25 variations of the french defense, yes that is the final 1 or 2% that might be the difference between 2500 rated players.   Knowing 2 variations of it from both white and black perspective however is extremely useful even as a 1300 rate player.   Knowing nothing at all... leads to getting into a bind and playing a losing game as an uphill struggle from move 5 onward.  A low rated player that knows one or two variations of 4 or 5 strong openings for 3-5 moves each has a strong advantage over the untrained.  

Yes, but you don't really need to study book moves for that, you'll pick them up going through annotated games and so on.

They game mentioned is not out of book at move three, its just a ECO 23 Closed Sicilian.  I just see that book moves help coordinate your pieces to squares that are most effective and knowing why they are best (book) is due to results.  Most book moves are doing the same thing either its classical or hyper-modern style of play.

I was out of book on move three, meaning that I knew 3...Nd4 was OK but had to invent the rest myself. Which isn't that much of a problem, opening moves are easier to find than middlegame moves in my experience.

At 1300 level you should get by just by knowing the general opening principles imo. Even for stronger players it's much more important to understand the general ideas of the opening setups and typical plans for the resulting middlegame positions than remember every line in conrete detail. Admittedly remembering concrete details helps though.

Actually I've noticed in my own games that sometimes it's better to know nothing about a variation than to have just a vague idea. I've played some moves just because it's theory to find out that I understand nothing about the resulting position or that it was possible in some very similar postion but fails miserably in the current case. If I would have been able to look at the position unhindered by the weight of the theory I'd probably have noticed that the move doesn't work or it would've never occured to me in the first place because I don't understand the reasons behind it. Instead I'd been able to make some other entirely reasonable move.

Both players were waisting important tempo moves to get there pieces out early and by move 5 black would have had a doubled pawn by not exchanging knights? All those ideas even for a fair player are very valuable during the course of the game.

So are book moves good?

Only if you understand WHY they are being played. Memorizing lines "because Magnus plays that" is worse than useless.