Middle Game

  At the moment I seem to struggle on my middle games in chess, and I feel the reason to this is because of my lack of knowledge in middle game chess theory and middle game strategy. This leads me to the question on what are the chess theories that I must know to improve my middle game and how can I improve my middle game strategy?

ps: My blitz rating is in the 1100's and my rapid is in the 1200's.

Possibly of interest:
Simple Attacking Plans by Fred Wilson (2012)
https://web.archive.org/web/20140708090402/http://www.chesscafe.com/text/review874.pdf
Logical Chess: Move by Move by Irving Chernev (1957)
https://web.archive.org/web/20140708104437/http://www.chesscafe.com/text/logichess.pdf
The Most Instructive Games of Chess Ever Played by Irving Chernev (1965)
https://chessbookreviews.wordpress.com/tag/most-instructive-games-of-chess-ever-played/
Seirawan stuff
http://seagaard.dk/review/eng/bo_beginner/ev_winning_chess.asp?KATID=BO&ID=BO-Beginner
http://www.nystar.com/tamarkin/review1.htm
50 Essential Chess Lessons by Steve Giddins
https://web.archive.org/web/20140708100833/http://www.chesscafe.com/text/review534.pdf
Simple Chess by Michael Stean
https://web.archive.org/web/20140708104258/http://www.chesscafe.com/text/review400.pdf
Amateur's Mind by Jeremy Silman
https://web.archive.org/web/20140708094419/http://www.chesscafe.com/text/ammind.pdf
Chess Secrets: The Giants of Chess Strategy by Neil McDonald
https://web.archive.org/web/20140708092313/http://www.chesscafe.com/text/review620.pdf
Chess Strategy for Club Players by Herman Grooten
https://web.archive.org/web/20140708101926/http://www.chesscafe.com/text/review696.pdf
Chess Training for Post-beginners by Yaroslav Srokovski
https://web.archive.org/web/20140712013538/http://www.chesscafe.com/text/review945.pdf
Chess Strategy: Move by Move by Adam Hunt
https://web.archive.org/web/20140708093249/http://www.chesscafe.com/text/review890.pdf
How to Reassess Your Chess (4th ed.) by Jeremy Silman
https://web.archive.org/web/20140708095832/http://www.chesscafe.com/text/review769.pdf
Winning Pawn Structures by GM Alexander Baburin (1998)
https://web.archive.org/web/20140718055446/http://chesscafe.com/text/wps.txt
Understanding Pawn Play in Chess by GM Drazen Marovic (2000)
https://web.archive.org/web/20140708110136/http://www.chesscafe.com/text/review249.pdf
Dynamic Pawn Play in Chess by GM Drazen Marovic (2001)
http://theweekinchess.com/john-watson-reviews/books-of-many-flavours
Winning Chess Middlegames, An Essential Guide to Pawn Structures by GM Ivan Sokolov (2009)
https://web.archive.org/web/20140708091955/http://www.chesscafe.com/text/review676.pdf
Pawn Structure Chess by GM Andrew Soltis (2013)
https://web.archive.org/web/20140708101523/http://www.chesscafe.com/text/review908.pdf
Chess Structures - A Grandmaster Guide by GM Mauricio Flores Rios (2015)
"There is also masses of stuff in the book that made me go 'Oooh!' and 'Aaah!' so I think it will have the same effect on you! In particular, I loved Rios' exposition of White's plan of exerting queenside pressure against Hedgehog systems. I'd seen one of the games he quotes in his chapter but I'd never remotely made any link to a structured way of fighting the Hedgehog structure, so this chapter was a real eye-opener for me ...
In conclusion, warmly recommended. Lots to learn!" - GM Matthew Sadler
https://www.newinchess.com/media/wysiwyg/product_pdf/7495.pdf
The Power of Pawns by GM Jörg Hickl (2016)
"The didactic concept of the book is admirable. Each chapter defines the structures, explains the typical characteristics and shows the plans for both White and Black. The reader participates by assessing positions and invariably receives useful tips for practical play." - FM Harry Schaack
https://chessbookreviews.wordpress.com/tag/the-power-of-pawns/
https://www.newinchess.com/media/wysiwyg/product_pdf/9034.pdf
Zurich 1953 by Bronstein
http://exeterchessclub.org.uk/content/review-zurich-1953-bronstein
Python Strategy by Tigran Petrosian
http://sagarteacheschess.blogspot.com/2015/09/python-strategy-book-review.html
Petrosian’s Legacy by Tigran Petrosian (1990)
https://web.archive.org/web/20140708103409/http://www.chesscafe.com/text/review309.pdf
Petrosian: Move by Move by Thomas Engqvist
"Engqvist gives us a rare treat and a genuine, sympathetic understanding of one of chess' greats who nowadays tends to gets lost in the shuffle!" - Michael Ciamarra (2014)
Grandmaster Chess Strategy by Jürgen Kaufeld & Guido Kern
https://web.archive.org/web/20140708093410/http://www.chesscafe.com/text/review812.pdf