It’s intriguing how Ian McEwan is able to turn a single fleeting event into a short novel. On Chesil Beach is about a couple of British newlyweds in 1962; Edward and Florence are virgins, very inexperienced when it comes to expressions of sexuality. All of these sexual inhibitions culminate as they attempt to have sex on their wedding night.
As the couple settles into their hotel room and awkwardly while away the time until they decide to have sex, McEwan goes backwards in time to explore their past. The two undoubtedly care for each other, but it is apparent that one major reason Edward proposed is so that they could finally have sex. He has anxiety about his inexperience, but is eager to finally consummate their relationship. Florence, on the other hand, has always been put off by the thought of sex. She loves Edward and made some sexual advances toward him during their courtship, but always did so out of preconceived notions about what was required of her as a girlfriend.
I’m hesitant to say much more than that so as not to give away the ending. I will say that the book is beautifully written; I was a little apprehensive of giving McEwan another shot after my dissapointment with Atonement. I’ve also seen some complaints about the length of the book—it’s a little too long to be a novella, but feels too short to be a novel—but I think the length was perfect; anything longer would have been pushing it.
Feminist Texican Reads 
I loved this book so much more than I did the longer McEwan works I’ve read (Atonement and Saturday). And I agree with you that a longer book would have been too much.
I’ve only read his Amsterdam and really didn’t like it at all. Maybe I should give him another chance.