Having just posted my top 10 (with wiggle room) on 4MA - I thought I'd repeat it here. Mind you, it's a thankless task having to pick an arbitrary number out of all the great books I've been lucky enough to read this year....
Naming the Bones, Louise Welsh
The Diggers Rest Hotel, Geoffrey McGeachin (Aust)
In the Dark, Mark Billingham
Gunshot Road, Adrian Hyland (Aust)
Harbour, John Ajvide Lindqvist
Hypothermia, Arnaldur Indridason
Watch the World Burn, Leah Giarratano (Aust)
Cut & Run, Alix Bosco (NZ)
Dark Blood, Stuart MacBride (UK)
The Anniversary Man, RJ Ellory
If I'd had headcount I would have added:
Thrill City, Leigh Redhead
A Few Right Thinking Men, Sulari Gentill
Where Have you Been? Wendy James
The Old School, P.M. Newton
Let the Dead Lie, Malla Nunn
Trick of the Dark, Val McDermid
Madigan Mine, Kirstyn McDermott
Golden Relic, Lindy Cameron
The Half-Child, Angela Savage
But as I said - it's a thankless task and there were lots of fantastic books in 2010.