Might be the wrong URL for Next. Correct:
Snowman, while standalone, is not the first Harry Hole novel by Nesbo. It was the first Hole book I read but some things are better understood if you've read the Oslo trilogy first.
I thus nominate the first of the Oslo trilogy, The Redbreast by Jo Nesbo. http://inkmesh.com/ebooks/redbreast-...e)+by+Jo+Nesbo