I'm almost done with the Silmarillion, and I would really like to know more about Numenor and it's history. Which books should I read?
I'm still going through Tolkien's catalog myself and learning, so if any of this is off, please feel free to correct me >.<
The best source for more Numenorean history is Unfinished Tales, as it is literally titled Unfinished Tales of Numenor and Middle Earth. It tells of Numenor before its inevitable downfall.
Also, History of Middle Earth will have stories of Numenor and the Edain, but they are "fringe canon", often Tolkien's first drafts of later works. It's a 12-book encyclopedia of Tolkien's works, and is really interesting for Tolkien scholars and those who want to have a deep understanding of his works.
If you just like Edain in general, I'd recommend is the Children of Hurin, it's basically a full-length novel detailing the chapters in the Silm about Turin, Hurin, Nienor & co. I really enjoy it, it's more in the style of LotR than the Silm if you prefer that.
And of course, if you haven't read Lord of the Rings yet, it's not /strictly/ Numenor, but it's pretty much about the redemption of men and the coming of the Fourth Age. (I'm sure you know this already :P)