I bought The Ideas Behind the Chess Openings Link although I bought an older 1970s book rather than the one in the link.
It’s really a great book, my version is in the older chess notation and I set up a board on my bed to play through all of the openings. I’m now using D4 as my primary opening.
I’m thinking of buying his end game and middle game books as well. Are the equally worthwhile to add to my collection? I play primarily online, but I also like to play in coffeehouses.