Too much to read! It can be quite boring to read some of it in its entirety anyways. Some modules are worth reading, especially if I'm planning to
DM one. And there are a few books & modules that really stand out.
With respect to what edition, 1st is my preference, although the 3.0/3.5 edition items are usually written quite well. 2nd, eh - it's okay. More like novels and the detail is usually quite extensive.
With respect to a world/setting, Greyhawk is the clear preference for me. I just been developing in it for too long. I do enjoy some of the material written for Forgotten Realms though.