improvement

Possibly helpful:
Simple Attacking Plans by Fred Wilson (2012)
https://web.archive.org/web/20140708090402/http://www.chesscafe.com/text/review874.pdf
https://www.newinchess.com/Shop/Images/Pdfs/7192.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/
Winning Chess by Irving Chernev and Fred Reinfeld (1949)
https://web.archive.org/web/20140708093415/http://www.chesscafe.com/text/review919.pdf
Discovering Chess Openings by GM John Emms (2006)
https://web.archive.org/web/20140627114655/http://www.chesscafe.com/text/hansen91.pdf
Openings for Amateurs by Pete Tamburro (2014)
http://kenilworthian.blogspot.com/2014/05/review-of-pete-tamburros-openings-for.html
Chess Endgames for Kids by Karsten Müller (2015)
https://chessbookreviews.wordpress.com/tag/chess-endgames-for-kids/
http://www.gambitbooks.com/pdfs/Chess_Endgames_for_Kids.pdf
A Guide to Chess Improvement by Dan Heisman (2010)
https://web.archive.org/web/20140708105628/http://www.chesscafe.com/text/review781.pdf
Yeah, but you can always get a Chevy with the butterfly doors.
All of the above.
Playing helps develop good habits (like blunder checking) and exercise making practical decisions (playing 2nd best move to save time, playing moves that are difficult to respond to).
Doing drills helps retain memory (going over opening moves, or solutions to technical endgames) or helps recognize basic patterns quickly (solving tactical puzzles or endgame studies)
Studying gives you new knowledge (e.g. reading instructional books).
The broad categories are opening, strategy, tactics, endgame, and annotated game collection. Read one book in each of the 5 categories above (over the course of a few years). Do 30-60 minutes of drills each day, and play a little every day, and you'll improve many 100s of points.
Seirawan published a series of books for newer players. Here are 3:
https://www.amazon.com/Winning-Chess-Strategies-Everyman/dp/1857443853
https://www.amazon.com/Winning-Chess-Tactics-Everyman/dp/1857443861
https://www.amazon.com/Winning-Chess-Endings-Everyman/dp/1857443489