I won't bother with recounting the plot--plenty of others here have done that--but I will give some thoughts from the perspective of a 40-something who remembers fondly the movie and the times from whence it came.
I remember hating this movie when I first saw it back in the day. I'd read half the novel and hated that too. My main memory of both of them, oddly enough, was the Coma Baby. It features heavily in the book but somewhat less so in the movie.
Watching it again so many years later and so many years out from the 80s, I was surprised to find myself enjoying it. Perhaps it was a nostalgia thing. My mind was certainly flooding with associated memories. 1988 was the year I finished high school. I was soon to leave my little red-neck country town and move to the big smoke where a whole new life would begin (and there have been at least three more since then!).
Some positives: I'm a huge Donald Fagen/Steely Dan fan, so Fagen's soundtrack was appreciated. It doesn't really sound like his regular stuff (until the very end), and was, frankly, often quite cheesy and even out of place at times. But I convinced myself I liked it. Other Fagen fans may also. The movie really grabs the 80s very effectively. Nightclubs, hair, blow, the whole bit. There is a surprising appearance from the wonderful Jason Robards which, shamefully, is uncredited according to IMDb. Considering the size of his role this is kind of odd.
Negatives: Phoebe Cates seemed completely unconvincing as a model and Michael J. Fox was completely unconvincing as a...sorry, but, hey...as a grown-up. He's never really any different from how he was in Back to the Future or even Family Ties. He's still all got up in jeans and a suit jacket, skipping all over the place, and gulping, "Shucks" (at least seemingly). No disrespect to the guy. Just that this movie reminds that he was never so well suited to anything with pretensions to being serious. And that last point sums up the problems with this film: it eventually becomes apparent that the movie is trying to be taken seriously. It just doesn't work though. A pretentious novel as starting place doesn't help. Ham acting and cheese dialog don't help none neither.
Still, an enjoyable time capsule. Kiefer does OK as wise-a** friend. The wonderful Frances Sternhagen, an appearance from the then-soon-to-be-late John Houseman, and even the magnificent William Hickey. Tracy Pollan is gorgeous and Swoosie Kurtz is her usual charming self. The ending is quite poignant, featuring Dianne Wiest, but isn't enough to really justify getting there.
If you're 40-something, watch this with ice cream and snacks on a lazy weekday evening. If you're younger or older than that...probably don't bother, coz it ain't really that great.
