Which Middlegame Books Helped You Most?

Said above. Also you can post which ones you want, have heard good things about, or think can be good.

How to Reassess Your Chess by International Master Jeremy Silman is a great book that will help you understand the nuances of the middlegame better, the book does a great job at explaining complex concepts in a fairly easy to understand fashion, I'm not gonna speculate about rating gains, but I can assure you, you will be a better player after reading this book and chess won't feel misterious anymore to you regarding positional assessment.

This book alone won't make you a strong player, you'll still have to improve on your tactical awareness and endgames, I'd also suggest you to put opening study aside until you reach expert level... learn endgames, practice tactics and work on your positional assessment.

These were the things I had in mind @dekayi. I am studying endgames, could you suggest something for tactical awareness?

Lichess puzzles are great in my opinion, you have a puzzle dashboard (lichess.org/training/dashboard/30/dashboard) where you can see your strongs and weaknesses, review the tactics you missed and you can also choose the themes of the tactics you're practicing (lichess.org/training/themes), overall I'd suggest to stick to the "Healthy mix" but if you feel like you really need to improve on a specific area you could dedicate some extra time to it.

How to reassess your chess by Silman!

Hello, I didn't read Silman, instead I read John Nunn - it was dry to read, but very instructive, I can recommend it.

It was named "Understanding Chess Middlegames"

The most rating gain was likely from something by Reinfeld, like 'Complete Chess Course', because points are easy when you are low rated. I remember [from the 1970's so its foggy] reading books of Znosko-Borovsky and Pachman. Lots of us back then learned from Pachman. Right now I'm working thru books of Sokolov. They have very specific topics and are very good on their topic.

I really like the small book from Michael Steen - Simple Chess. He focussed on a few topics (Outposts, Weak Pawns, White square Strategy etc.) and makes the topic very clear. After this one, I feel ready for Silmans HTRYC.

I really like Simple Chess, too. It's very approachable but it definitely not simplistic - someone was saying that Boris Gelfand re-used one of Stean's examples (on "what does it actually mean to have a space advantage") in Positional Decision Making in Chess, which seems like quite a mark of respect!

I'm looking at Hellsten's Mastering Chess Strategy next - in fact, his whole set of Mastering Strategy books (opening, chess and endgame). From what I've seen of him on Youtube things he's a good teacher, the books get generally good reviews, and they seem to be based heavily in concrete examples and exercises, which I like.

complete, encompassing, and precise, not to forget fundamental.

From above, it seems the Stean approach might not be the first 2, but might be the last 2.

So that line of book approach (if there is more than one book, not fixating on one author, in hope that more than one could share approach, and also because I just can't remember names and titles etc..., include opening theory, by lexical order):
are there books that not just touch the correlations between opening classes and middle-games classes?
(if anybody could regroup opening theory)
classes=typology. could be "the idea" "the plan". or sets of plans, or sets of ideas...

my point is not whether it might be included if one scrutinize, decipher, extract and digest, but whether it might be the front of approach, that it would be in the table of content for example (Stean table of content does put the points first, right?).