Gr 4-6-Though marred by superficial treatment and patchy fact-checking, these introductions make inviting additions to collections for their unusually strong emphasis on Web resources. Each title presents a standard set of basic facts about the planet's discovery, physical structure, moons, and exploration-but opens with an annotated list of 30 relevant Web sites, accessible with a password through a dedicated portal provided by the publisher. Drawn from print as well as electronic sources, Feinstein's texts are dry but factual, though he does not mention missions to Mars that failed or were sponsored by agencies other than NASA. The color illustrations, many of which are unaltered screen shots, are more problematic, including a photo of Europa's surface that is billed as Jupiter's, another photo a few pages later that includes advertisements, and a wildly incorrect date for a painting in Mars. Still, these books should be popular with both interest- and assignment-driven readers, and, as the publisher promises to keep the webliographies up to date for five years, with librarians, too.-John Peters, New York Public Library Copyright 2005 Reed Business Information.