These colorful volumes from the ongoing Mystery Files series briefly present particular facets of high-interest subjects. Following the introduction to the broad topic, each book offers a dozen double-page presentations designed to intrigue readers. Unsolved! describes mysteries such as the identity of the Man in the Iron Mask, the fate of Amelia Earhart, and the disappearance of Malaysia Airlines Flight 370 in 2014. Each two-page section includes a few paragraphs of text, a short sidebar and at least two illustrations, often photos and/or period illustrations. Given the books' brevity and the broad scope of their subjects, it's not surprising that the content in each section is scanty. Still, readers interested in individual topics may be motivated to look elsewhere for more detailed information. Good supplementary materials for larger collections.