There are two main sources on Rachmaninov, first--"Letters", and second a book called "Rachmaninov in Memories of Contemporaries". No idea if they were translated from Russian, but those would give you the most idea as for Rachmaninov as a person, as well as many facts about many things of his life. Also, it'd put a lot of light on his work.
As for his recordings... well every single one is a jewel, even though I don't agree with some of his interpretations. There would be way too many to list. Just get a full RCA 10 CD set. You can't go wrong with that.
Just a little note of warning. In my opinion, there were only three pianists in the last century which I'd consider as the "greatests ever". Rachmaninov (again, IMO) was one of them, so use this information with extreme caution, keeping in mind I am quite baised in this case.