In slip case.
Each volume is a collection originally published in single comic book form.
bk. 1. 30 days of night
bk. 2. Dark days
bk. 3. Return to Barrow.
OBNB doesn't sell books, but you may be able to find a copy at one of these websites:
The 30 days of night trilogy by Steve Niles. ISBN 9781600101014. Published by IDW Publishing in 2007. Publication and catalogue information, links to buy online and reader comments.
