Anything by Golubev or Watson. Also books by the publisher Everyman.
Opening Books
Good Chess Openings Books for Beginners and Beyond....
https://www.chess.com/blog/RussBell/good-chess-openings-books-for-beginners-and-beyond
Oh behave, Middlegamer! O.K. Golubev's book on the dragon - still essential reading for both sides in that opening - also his videos on various openings are great If there is an opening in your repertoire that has an everyman book about it - the one on the Sicilian ..e6 systems, if I remember correctly - is very good. Watson's books on the english opening and the french defence are very good. It is a different question recommending opening books for 'beginners', rather than more experienced players, because actually - speaking as a former coach - 'beginners' need to study the opening in relation to the resultant middle game positions, rather than a mountain of theory. For that reason I would say that John Emm's book - The Easy Guide to the Ruy Lopez - is very good for 'beginners', who play 1.e4 as White, as it gives both the theory, and the themeatic ideas of the various lines. I would not recommend inexperienced players to look to much at 'repertoire books', tempting though it may be, as they often use sidelines that are not actually very good, and give them very skimpy coverage.
Ah! Now I see! Someone says ''what is a good book on the dragon?', then I say ''Golubev's book is good''. Forgive my senility!!😨
http://www.jeremysilman.com/shop/pc/Flexible-French-The-76p3490.htm
https://web.archive.org/web/20140627104235/http://www.chesscafe.com/text/hansen114.pdf
If that is not flexible enough, there is also:
http://www.jeremysilman.com/shop/pc/Even-More-Flexible-French-The-76p3908.htm
https://www.newinchess.com/media/wysiwyg/product_pdf/9010.pdf
... Grandmaster Repertoire Series French Books ...
https://www.newinchess.com/media/wysiwyg/product_pdf/7314.pdf
https://www.qualitychess.co.uk/ebooks/GM15-FrenchDefence2–excerpt.pdf
https://www.qualitychess.co.uk/ebooks/GM16-FrenchDefence3-excerpt.pdf
... Simon Williams [has] a series on chess.com about the French Defense
https://www.chess.com/video/player/why-simon-loves-the-french-the-advance-variation
https://www.chess.com/video/player/why-simon-loves-the-french-the-exchange-aka-the-groan-variation
https://www.chess.com/video/player/why-simon-loves-the-french-the-universal-system
https://www.chess.com/video/player/why-simon-loves-the-french-the-classical-variation
... Tatev Abrahamyan [has] a series on chess.com about the French Defense
https://www.chess.com/video/player/completely-french-the-winawer---part-1
https://www.chess.com/video/player/completely-french-nd2-variation
https://www.chess.com/video/player/completely-french-advance-variation
I would like to help the chess.com community by suggesting books, videos and other resources for all openings
. Just post a request below in the comments and it will appear here soon.
P.S. :- Make your requests based on a certain opening. For example :- Request Nimzo-Indian and it will appear here.