A fun and informative presentation of exactly what the title says. The illustrations are well-done, and the touches of humor with the mammoths is engaging and cute. I grabbed this book from one of my friends who was trying to clear out some shelves, and now I intend to pass this on to someone else who might enjoy it. I think it would be of interest to precocious kids of preteen through early teenage years, maybe as young as 6 or 7. I know I would have loved it when I was in early grade school. I like how it was organized starting with the simple machines, and building on the physical principles. It is definitely dated, with inclusions of dot matrix printers, typewriters, floppy discs, and discussion of megabytes of storage, but the vast majority of the machines are still relevant today, and the underlying physical principle are of course important.