Other than strategy books, learn about pawn structures and endgames.
Which books are best for you depends on your level.
If you're too new, then a lot of it wont seem very reliable until you can play most of your games without any big blunders.
For example, a book may give an example where white has a better placed rook and knight. The book might point out that to avoid it, black would have to accept too many weak pawns. But if the idea of losing a pawn or two at some undetermined point in the future doesn't seem like a big deal, then the ideas in the book won't seem very reliable to you.
Does anyone know where I can find self-paced training/practice in long-term strategy as opposed to tactics? Thanks in advance :)