I thought it was fabulous. I was was sucked in by the gorgeous writing from the first paragraph; the imagery placed me on the Riviera in 1925 and I continued to be beguiled by the subtle characterizations and the slow and indirect reveal of the story at the heart about the beautiful couple who so entranced Rosemary at her first glimpse of them.
It's both a very American and very Fitzgeraldian story, about disintegration and second acts and who gets to have them (Grant in Galena) and who doesn't, about people who use others, those who observe and those who act. Other themes include that of Amerians abroad, Americans and race, I could go on and on. I thought it was very dense, much more so than The Great Gatsby.
For all that it's supposed to be about Gerald and Sara Murphy, it's obvious that it's more about Scott and Zelda. Presumably Fitzgerald was engaging in projection/aspiration. I have New Critic tendencies that don't like to delve to deeply into these origins, but I'm mentioning it for those who find the shift from Murphy to Fitzgerald a little disconcerting and unjustified. I think it worked, myself.
IMO, the book wouldn't have been nearly so effective told chronologically. We would have missed the slow reveal and the outsider's perspective of the Divers, which can be expected to be flawed, unlike that of an omniscient narrator. What was Malcolm Cowley thinking?
I know a lot of posters didn't care for it at all and I'll be interested to read their reactions. I couldn't put it down.