I thought of Ron because I had just read Caro's LBJ series recently and had Presidential bios on my mind :) Caro is a good read in that area, and also Kenneth Davis' bio of FDR, David McCullough's bio of Truman, and Stephen Ambrose's bios of Eisenhower and Nixon.
I've read the first two in Caro's series about LBJ. As much as I love Reagan, I kinda lived through a lot of that. So I'd like something less familiar.