What To Read?

Got an email the other day from a recent college grad who is working as editor for a cool blog. He's reading lots of bits and pieces of stuff every day, but he's wondering about reading in his downtime. Here's a snippet of his letter:

There are so many books, so many great essays and magazine pieces, that I never really know what to read. I want to read great writing that I'll enjoy, but, more importantly, great writing that'll make me better. Should I be reading fiction, poetry, or just nonfiction? I don't really know. Should I be reading a book? Should I just be reading magazine stuff? If you can't tell, I'm kind of all over the place here.

What I'm really looking for here is some direction. I'm a nonfiction writer, who wants to read stuff that will make his writing better. Is there any kind of reading pattern or something that you recommend? Are there certain books you'd say I should read before any others? Is there a list of magazine stuff I need to read? Should I focus on more recent stuff (Best Americans, maybe?) or both older and newer?

It's not that I'm not reading. I am, but I still can't shake the feeling that there's something else I should be reading. If you could give me any direction, that would be great. Did you used to feel this way? Do you still? I'd appreciate any help. Sorry for all the questions. I look forward to hearing from you.

So, let's help a brother out.