From this year, without a doubt The Heart's Invisible Furies - John Boyne
From my all time list :
Star of The Sea - Joseph O'Connor
Middlesex - Jeffrey Euginides
The Poisonwood Bible - Barbara Kingsolver
The Quincunx - Charles Palliser
The Crimson Petal and the White - Michel Faber
The Blind Assassin - Margaret Attwood
The Goldfinch - Donna Tart
Life After Life - Kate Atkinson
The Hidden Garden - Kate Morton
Asta's Book - Barbara Vine
It's hard to pick one
Two books that I finished and wished I hadn't bothered, Lincoln in the Bardo - George Saunders and Autumn - Ali Smith, both so awful, worse than homework! Booker Prize Winners I believe, but then again so was the sublime Blind Assassin which I loved.
Couldn't finish Jonathan Strange and Mr Norrell, just too long, I don't mind a tome, but I have to be engaged with it to invest the time.