I can't recommend this book enough. Cul de Sac is the daily comic strip successor to the Peanuts, Calvin & Hobbes, etc., line that we've all been waiting for. You should buy it now.
UPDATE: RIchard Thompson twittered that this was now available to order on Amazon, but on closer examination it looks like it's only available for PRE-order. Consider this a test of the Cul de Sac Golden Treasury Annoucement System. When the book is actually available you will receive further instructions.
UPDATEST: IT'S NOW AVAILABLE!