I've read Marilynne Robinson's other book, Housekeeping, when it was on the Diane Rehm book club back a few years ago. I really didn't get that book, so I can say that this one is a great improvement over that.
Gilead is good, but very very slow. It takes most of the book to get to the meat of it, & by then you're almost too frustrated to care. The story is about a man in his 70's who's going to die soon--he has a heart condition. It's the 1950's in Iowa, he's a preacher (though I never really figured out of what religion), & he has a young son that he never thought he would have. The whole book is a journal that the man is writing for his son, so he'll have some idea what his father was like when he's grown. It's a very nice book, well written. I'm just not used to the extremely slow pace, I think. One of the characters, Jack Boughton, is memorable in that he's flawed. Everyone else seems to be so very well behaved, though we really don't get to know about John Ames' wife. Jack's character was the best part of the book for me. I, like most of us, like my story heroes flawed. And Jack is flawed. But of course, tries his damnedest.
If you can handle the slow pace, I highly recommend this one.