Since the company that now owns
Dungeons & Dragons is putting most of their outdated, out of print backlog up for sale as pdf, I got myself the Rules Cylopedia which is currently
on sale for $10.
It's a very interesting read. Years back in 1978, they made the descision to branch D&D in two separate games. The old Basic Game and the much more complex
Advanced Dungeons & Dragons. The AD&D line kept being the star and was continuously developed further to this very day (though they just call it D&D again now), while the Basic Game drifted into obscurity and has been discontinued for almost 20 years now.
The Rules Cyclopedia is a compilation of the last version of the Basic Rules that includes almost all the upgrades that were later added to it. To anyone familiar with D&D, this one seems very familiar too and you can easily tell that it's D&D. But it's also pretty different in many ways, especially the entire visual style and atmosphere. It's an alternative evolution of the original game that happened almost entirely independent and I can see why it still has a good number of big fans. It's a lot easier than any other version of D&D with much less rules and special abilities, which make it a lot more ssuited for playing games where the players are exploring the world and interacting with the people instead of focusing a lot on lots of big battles with all kinds of tactical planning.