I’ve often recommended this book by CJS Purdy as being one of the most readable and offering some of the best advice I’ve ever read. The book is actually a collection of Purdy’s magazine articles and as a bonus it contains his biography and a collection of his best games. What I really like is that you can open it up to any page, read an article and actually learn something. Purdy also had a knack for actually explaining things with words rather than just presenting the reader with long lines of analysis and saying “White is better.”
The Search for Chess Perfection
TRANSITION FROM THE OPENING TO MIDDLEGAME
The transition from opening to middlegame, while not inherently a more difficult stage of the game than others, is one in which most players feel their deficiencies very keenly. For it is here that they take the plunge from known paths into the jungle.
After having started with a cut-and-dried strategical aim-development-they have to find a new aim, and that aim depends entirely on the position.
But stop a minute! Have you really completed your development? What about that K’s R still on fl/f8? He's not doing anything there, and you can't open the f-file. You say, "Oh, but there's no good file to put him on." What about the d-file? "But my own pawn is in the way on d4/d5; what could the Rook do on d1/d8?"
The answer is that he can't do anything. But the idea is to place him in the position of maximum readiness; to be more specific, place him on the file that is most likely to become open. For example, in the Queen's Gambit Declined a good player with White knows that Black is bound to want to play ... c5 sooner or later, so that he can look forward to the d-file becoming open in the fullness of time. Therefore White usually plays his K’s R to d1; the other R has normally gone to c1, because the c-file already becomes openable after the move c4 against ... d5.
As a general rule, the player who gets his R’s ready for the future, restraining himself from premature attack, is very wise. Time and again you will see masters break this rule, but it is best not to break it yourself without a clearly good reason. Don't break it just because there are no open files.
Certainly it does sometimes happen that the opening makes no good places for the R’s.. In the Giuoco Piano, for instance, with the N’s on c3/c6/f31f6 both sides are blocked from playing either d4/d5 or f4/f5. One player has to undertake the business of opening a file up for himself and his opponent, and that is why, in such an opening, the first move ceases to be an advantage. Prefer an opening that makes the provision for a P exchange in the center (as nearly all openings do).
Well, let us suppose that you really have developed your R’s, or else you have a really good reason for interrupting that development; in other words, the middle game may be said to have started.
The thing to do now is to discover a good strategical aim. Is it? No, any reader who has paid any attention to my effusions in the past will know that the first thing at every move is a look round the board for any possibilities of a combination (a forcing line of play), and if any appear, to examine them to see if any of them is sound.