I don't know about this book.
On one hand, when all is said and done the narrative feels simply like an intricately-written case study, though occasionally punctuated with inconsistently glorious descriptions, for an odd psychological disorder that even with all of Ian McEwan's brilliance is still only mildly interesting.
On the other hand, it's McEwan's wonderful writing combined with a first-person perspective, which gives us the rare treat of a character reflecting introspectively using all of McEwan's power with words.
Now and again I was reminded of Paul Auster - the hints at future calamities and complications prior to their being actually narrated, the ambiguity as to whether events are real or imagined, the questioning of the protagonist's sanity.
Like Auster (but so much better), McEwan has a special talent for turning order into disorder. Strangely, in this book things return to some degree of order at the end; I'm used to there being no loose ends at the end of a McEwan novel, but usually it's because everyone's dead or something. I hate to imply that the ending was too happy just because it wasn't completely hopelessly tragic; it was more that it seemed plucked from thin air.
Definitely a 2.5-star book.