It's impossible to answer your question without some idea of your playing strength and experience. There are hundreds of good books out there, but most will be too advanced or too basic for your current level. Please tell us more about your chess history, and someone will surely be able to make good suggestions.
Chess books on the middle game and end game
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https://www.chess.com/article/view/test-your-positional-chess
https://www.chess.com/article/view/do-you-really-understand-positional-chess
https://www.chess.com/article/view/get-ready-to-test-your-positional-chess-again
Simple Attacking Plans by Fred Wilson (2012)
https://web.archive.org/web/20140708090402/http://www.chesscafe.com/text/review874.pdf
http://dev.jeremysilman.com/shop/pc/Simple-Attacking-Plans-77p3731.htm
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/
http://store.doverpublications.com/0486273024.html
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
http://www.gambitbooks.com/pdfs/50_Essential_Chess_Lessons.pdf
Simple Chess by Michael Stean
https://web.archive.org/web/20140708104258/http://www.chesscafe.com/text/review400.pdf
http://store.doverpublications.com/0486424200.html
Amateur's Mind by Jeremy Silman
https://web.archive.org/web/20140708094419/http://www.chesscafe.com/text/ammind.pdf
https://www.silmanjamespress.com/shop/chess/amateurs-mind-the-2nd-edition/
Chess for Hawks
https://www.newinchess.com/media/wysiwyg/product_pdf/9041.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
https://www.silmanjamespress.com/shop/chess/how-to-reassess-your-chess-4th-edition/
Chess Strategy for Club Players by Herman Grooten
https://web.archive.org/web/20140708101926/http://www.chesscafe.com/text/review696.pdf
Pawn Structure Chess by GM Andrew Soltis (2013)
https://web.archive.org/web/20140708101523/http://www.chesscafe.com/text/review908.pdf
The Power of Pawns by GM Jörg Hickl (2016)
https://chessbookreviews.wordpress.com/tag/the-power-of-pawns/
https://www.newinchess.com/media/wysiwyg/product_pdf/9034.pdf
Modern Chess Strategy
http://store.doverpublications.com/0486202909.html
Silman's Complete Endgame Course
http://theweekinchess.com/john-watson-reviews/theres-an-end-to-it-all
https://web.archive.org/web/20140708103149/http://www.chesscafe.com/text/review594.pdf
https://www.silmanjamespress.com/shop/chess/silmans-complete-endgame-course/
books by max euwe on middlegame are best in 2 volumes
My system by Aron Nimzowitch and Pawn Power In Chessby Hans Kmoch. Every chess player should have a copy of these books
Good Chess Books for Beginners and Beyond...
https://www.chess.com/blog/RussBell/good-chess-books-for-beginners-and-beyond
One can get some idea of the lasting scope of the respect for My System by looking at:
https://www.chess.com/article/view/the-best-chess-books-ever
Still, it might be noted that My System apparently did not occur to GM Yasser Seirawan as something to include in his list of personal favorites, and Aaron Nimzowitsch was not identified by the GM as a very worthy author.
https://www.chess.com/blog/RoaringPawn/an-open-letter-to-the-four-time-us-chess-champion-gm-yasser-seirawan
https://www.chess.com/blog/GMYAZ/open-letter-response-user-radovics-letter-to-me
My System has accumulated some direct negative commentary over the years.
"... I found [the books of Aaron Nimzowitsch to be] very difficult to read or understand. ... [Nimzowitsch: A Reappraisal by Raymond Keene explains his] thinking and influence on the modern game in a far more lucid and accessible way. ... The books that are most highly thought of are not necessarily the most useful. Go with those that you find to be readable; ..." - GM Nigel Davies (2010)
In 2016, IM pfren wrote:
"My System is an iconoclastic book. A lot of things in there is sheer provocation, and it does need an expereienced player to know what exactly must be taken at its face value.
I love 'My System', and I have read it cover to cover one dozen times, but suggesting it to a class player is an entirely different matter."
Also: "[Some things] ARE wrong, and it's not easy for a non-advanced player to discover those wrong claims.
Nigel Short has claimed that 'My System' should be banned. Stratos Grivas says that the book is very bad. I don't share their opinion, but I am pretty sure that there are more useful reads for class players out there."
Although he is a fan of My System, IM John Watson similarly acknowledged (2013) that:
"... Not everything in it has stood the test of time, ..."
http://theweekinchess.com/john-watson-reviews/john-watson-book-review-108-of-eplus-books-part-2-nimzowitsch-classics
One last point to keep in mind is that, even if My System would eventually help a player, it might not necessarily be helpful to a player now.
"... Just because a book contains lots of information that you don’t know, it doesn’t necessarily mean that it will be extremely helpful in making you better at this point in your chess development. ..." - Dan Heisman (2001)
https://web.archive.org/web/20140626180930/http://www.chesscafe.com/text/heisman06.pdf
A My System sample can be seen at:
https://www.qualitychess.co.uk/ebooks/MySystem-excerpt.pdf
A Chess Praxis sample can be seen at:
https://www.qualitychess.co.uk/ebooks/ChessPraxis-excerpt.pdf
Various samples:
https://www.newinchess.com/media/wysiwyg/product_pdf/9027.pdf
RussBell wrote (June 1, 2019):
"My System is of course one of the great masterpieces of chess literature, compulsory reading for generations of players...I recommend My System[...]as strongly as I do any other chess book. These days most classic works are no longer essential to a chess education, especially since the Internet; but if there's an exception, Nimzowitch's work is it." - from IM John Watson's book review here...
https://theweekinchess.com/john-watson-reviews/john-watson-book-review-108-of-eplus-books-part-2-nimzowitsch-classics
Perspective on Aron Nimzowitsch's "My System"...
RussBell wrote (~9 days ago):
The following is Yasser Seirawan's Introduction to the Lou Hays 21st Century Edition of Aron Nimzowitsch's "My System", published November 1991. In this introduction he describes his earlier misgivings regarding the book, then continues by praising not only the Lou Hays edition of the book, but "My System" in general....(note particularly his comments in the third from the last paragraph ... ["This then is the strength of My System. It is a book that provokes you to think differently about chess. It challenges you to consider a different approach and urges you to prove or refute Nimzowitsch's ideas. It is also a book that you can read and reread, each time coming away with different lessons and insights, leading to a deeper understanding of the game." - GM Yasser Seirawan (1991)]
...
The following is a scathing criticism of Nimzowitsch's "My System" by Yasser Seirawan (penned in 2018, in response to an open criticism of his apparently prior vocal criticisms of Nimzowitsch, and his book)...
https://www.chess.com/blog/GMYAZ/open-letter-response-user-radovics-letter-to-me
So what are we to make of it - on the one hand Seirawan praises Nimzowitsch and his book, then later excoriates them both....
You be the judge...
https://www.chess.com/forum/view/general/which-book-should-i-read-first
In a previous discussion, someone reported a passage from Pawn Power in Chess by Kmoch: "The lengthening of the rearspan is often favorable, inasmuch as the expansion of territory behind the pawn increases the freedom of the pieces. By the same token, the shortening of the frontspan limits the freedom of the opposing pieces."
I'm not exactly a big fan of that sort of writing, but there nevertheless seems to be a widespread opinion that the Kmoch book is worthwhile.
"... [Pawn Power in Chess] should be on everyone's list [of favourites]. ..." - GM Nigel Davies (2010)
Another point of view:
"... Hans Kmoch’s Pawn Power in Chess is considered a classic by many. Nonetheless, most people found it daunting and confusing, given its weird terminology. Also the scope of the book was more theoretical than practical; not an easy book to read and study with. ... must be frustrating to read and study from for those rated below 1700. ..." - Stephen Ham (2000)
https://web.archive.org/web/20140708110136/http://www.chesscafe.com/text/review249.pdf
One can see a sample at:
http://store.doverpublications.com/0486264866.html
I have just landed on your website.please can you recommend of some good chess books on the middle game and end game? So far i only have books on the opening