Saturday is an elegant, absorbing novel that does not deserve to win the Booker. Since it is probably the most reviewed novel on the longlist, and since I am at present suffering from some malicious flu-thing that refuses to go away, I'll keep my comments brief.
Good points first. Ian McEwan's prose is elegant and understated. He is brilliant at describing things and places. I love the way he uses music, as both theme and texture. He excels at evoking the peculiar rhythms of everyday life, the sights and sounds and smells of the city. I like the capaciousness of the book, the fact that there is just so much going on, and I like that the central character, successful London neurosurgeon Henry Perowne, is both observant and complex enough to bear the weight of so much detail.
Yet for all this Saturday just didn't do it for me. The explicit politics are distracting, and not particularly interesting. Perowne aside, the characters are flat, predictable. The plot is neat, which is not a criticism in itself, but the way McEwan ties it all up is, frankly, silly. The book simply doesn't gel. It's full of interesting things, but McEwan can't make it work.
Despite these reservations, Saturday remains an engaging, often entertaining read. McEwan has at least tried something bold and different, and what is more he has partially succeeded, which is more than can be said for some.
Postscript: Reviewing Saturday in the New York Review of Books, your hero and mine John Banville describes it as "dismayingly bad". The review is not available online, but there is a fantastic riposte to it here that is also an astute review in itself.