This intriguing compendium of facts in the I Didn't Know That series encompasses the earliest paper boats of the Egyptians to modern day plastic-hulled Minesweepers. True to series format, each spread, beginning with the phrase ""I didn't know that,"" focuses on a specific era. Included throughout the book are the feature icons (searchand-find activities, true/false queries, etc.) to test readers' knowledge. The design doesn't intrude here (see review, above), perhaps because the topic is more immediately familiar to children. Watton and Moore's detailed illustrations are realistically rendered; the full-color panoramas, overlaid with many smaller pictures, invite in-depth perusals.