The Dangerous Book for Boys, by Conn and Hal Iggulden is a guidebook published by HarperCollins, aimed at boys "from eight to eighty." It covers around eighty topics, including how to build a treehouse, grow a crystal, or tell direction with a watch. Also included are famous quotes, stories, historical battles, and phrases that "every boy should know." It was published in the UK in June 2006, and reached number one in the UK non-fiction charts several times, selling over half a million copies.