I voted for FOTR, as a large chunk of that book takes place in the Shire and in the Wild—places that seem familiar (and comforting) to me as a native Mainer.
As for the Silmarillion, I didn't get far the first time I tried reading it, mainly because the lack of dialogue made it seem very dense to me. But later on, after I'd gotten deeper into the world of Middle-Earth, I went back and tried again, and I found it pretty fascinating—especially since Tolkien was a Christian, as am I, so the entire Illuvatar/creation aspect was very intriguing.