There is no book like Nimzovich's My System. Most people read it in increments instead of cover to cover. The second part chess praxis is also good. Pawn power in chess by Kmoch is excellent for pawn study but, as far as positional book, I think the best I read was a book by Samuel Reshevsky. I forgot the name now as years have passed but, what a wonderful book it was!
What's the best chess positional book?

THE AMERICAN CHESSPLAYERS HANDBOOK ... author is Howard Staunton. players rated 1500- 2000 can benfit reading and digesting the material. the other books mentioned are simpler to read.

There is no book like Nimzovich's My System. Most people read it in increments instead of cover to cover. The second part chess praxis is also good. Pawn power in chess by Kmoch is excellent for pawn study but, as far as positional book, I think the best I read was a book by Samuel Reshevsky. I forgot the name now as years have passed but, what a wonderful book it was!
The Art of Positional Chess...
It's a very good book for developing players... I don't think books hold a candle to the videos on Chess.com though.

I dont think My System is designed for a certain strength of player. More of giving guidelines as to what one is looking for. @ rated lower than you, The Art of Positional chess by Reshevsky?
Some possibilities at various levels:
50 Essential Chess Lessons by Steve Giddins
https://web.archive.org/web/20140708100833/http://www.chesscafe.com/text/review534.pdf
Chess Strategy for Kids by Thomas Engqvist
http://www.gambitbooks.com/pdfs/Chess_Strategy_for_Kids.pdf
Starting Out: Attacking Play by James Plaskett
https://web.archive.org/web/20140708101549/http://www.chesscafe.com/text/review467.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
Winning Chess Strategies
http://seagaard.dk/review/eng/bo_beginner/ev_winning_chess.asp?KATID=BO&ID=BO-Beginner
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
Understanding Chess Middlegames by GM John Nunn
https://web.archive.org/web/20140627012322/http://www.chesscafe.com/text/hansen154.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
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
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.
Also, 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."
"[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 sample of My System can be seen at:
http://www.qualitychess.co.uk/ebooks/MySystem-excerpt.pdf
... as far as positional book, I think the best I read was a book by Samuel Reshevsky. I forgot the name now as years have passed but, what a wonderful book it was!
The Art of Positional Chess...
It's a very good book for developing players... ...
I think the title is usually given as The Art of Positional Play. I believe that I have also seen the title as The Art of Positional Play in Chess. It was originally in descriptive (1 P-K4 P-K4) notation, but, somewhere along the way, an algebraic (1 e4 e5) revision was created. Another Reshevsky book was a collection of his games.
THE AMERICAN CHESSPLAYERS HANDBOOK ... author is Howard Staunton. players rated 1500- 2000 can benfit reading and digesting the material. the other books mentioned are simpler to read.
"... Wilhelm Steinitz, first world champion, almost single-handedly established the ground-rules for modern positional chess. ..." - IM Craig Pritchett (2011)

I've been thinking of reading My Great Predecessors series by Kasparov. Has anyone read it? Is it useful for positional improvement?

I bought (but didn't read yet) following book:
Simple Chess: New Algebraic Edition
More than a lesson in chess fundamentals, this book illustrates an increasingly prevalent and successful style of play — a method that begins by slowly accumulating small but permanent advantages, saving the outright attack for later in the game. Newly converted into the current algebraic chess notation, this edition of Simple Chess offers a strategic weapon for players at every level of expertise."

I've been thinking of reading My Great Predecessors series by Kasparov. Has anyone read it? Is it useful for positional improvement?
I haven't read them. I've heard GMs say they're good, and I've heard they have tons of analysis... so probably they're good but a lot of work.
See my post below

I am mostly thinking of buying the book Chess Strategy by Herman Grooten. Is it worth it?
hi sevenstarmantis,
yes i can recommend that book. I just bought it for kindle and it's kind of inspiring, not just lots of annotations.
What do you think it is? Personally I have read around 4 important ones: My System, How to Reasess you chess 4th edition, The Amateur's Mind, and The Complete Manual of positional chess. I think How to Reasses your chess and the Amateur's mind has helped me a lot. Also, consider me a strong class A player. Anyways, what do you guys think?