Similar to others in the "How Did We Find Out About _____ ?" series, this helpful introduction uses a historical approach to learning about science. The prolific Asimov makes the straight facts more intriguing by describing misconceptions and discoveries about blood from Hippocrates' day to the present. The progression of medical enlightenment unravels like a mystery readers learn about the workings of the heart, the circulatory system, and blood composition. Clear illustrations complement a logical presentation, and the pronunciation of difficult words is effectively placed within the text. Circulatory Systems by Alvin and Virginia Silverstein covers the same information in more depth, but libraries needing an extra title will find this a solid addition.