Kotaku put up an article about the history of D&D, and Dave Arneson and Gary Gygax.
It is bound to be a bit contentious . . . it feels like pot-stirring in a way. But if you haven't really delved into the history of the development of D&D, this is a place to get some of that information.
Dungeons & Deceptions: The First D&D Players Push Back On The Legend Of Gary Gygax
TL;DR version? Gary Gygax and Dave Arneson are both responsible for the hobby, and it didn't develop without a lot of rancor and credit-taking.
It's definitely worth reading. I'd also suggest Jon Peterson's Playing at the World, but that's a bit more of an academic look at the subject. I don't meant that as criticism. It's just aiming for telling the whole story in detail, and examining the development of role-playing games overall, not just telling the popular story of Gygax and Arneson and D&D.
And it's worth noting, that if you ever find yourself wondering at the friction, divisiveness, credit-warring, and hate that goes on in gaming and think, "Why can't we all just get along and play games with fireballs and elves?" Well, it was never the case that gaming was free of that. All of that nonsense is embedded in its history like original sin.