His memoirs are a fairly good read. Biography-wise you're going to run into the pro/anti Nixon stuff. Usually you can tell by the title (Arrogance of Power, The Invincible Quest, etc.), Nixon Agonistes is really quite good but only goes up to his presidency. The reason to consider it is that it shines a light on the fact that Nixon had some influential detractors who were quite well connected even before he was elected. EDIT (He had the detractors well before he was elected...though they were also well connected before he was elected too).

I don't want to weigh you down with a huge reading list, but those are a good place to start in order to at least get an idea of his picture of himself, and the weird distortions the occur in the field of Nixonography. Just avoid Schleshinger, I don't think he ever stopped lovingly fawning over the Kennedys long enough to form a coherent thought on anything else.

The Caro books are excellent. I'm in the middle of volume 2. His book on Robert Moses was an amazing read!