there are a few good books that might be good for you, but depending on how strong you are... idk. but these will almost def help you:
Have you read Reassess my Chess by Jeremy Silman?
Have you read My System by Aron Nimzowitsch?
also, how good is your opening theory, if youre training tactics a lot but not getting better at chess it may be cause your not implementing a proper plan from the beginning of the game. this may or may not help, im far from an expert
Hey, so i am an expert level player that has been constantly trying to reach a master level of chess knowledge. Now since it is summer, i have lots of free time to improve but as many tactics as i solve or as many positional problems that i solve, i can't notice any improvements. Does anyone have any suggestions that i could try out that might show any sort of improvements in my chess?