The National Air and Space Museum: Astronaut, Balloon, Comet

""Ee'' is for Earth, and there is a photograph of the planet taken by the Apollo 17 spacecraft. ``Nn'' is for Night Sky, ``Oo'' for Observatory, represented by undistinguished photos of the Milky Way and the most powerful telescopes in the world. The observatory itself is hardly visible. Entries sometimes span two pagesand two letterswhich will confuse ABC learners. Problems with the first books in the seriesone based on the Museum of Fine Arts in Boston and one on the Museum of Modern Art in New Yorkapply here: older readers, interested in the subject, will probably be put off by the ABC format, while the book's tall, narrow shape is difficult for small hands to grasp. And this title is more loosely organized than its predecessors; it's not clear if the objects (computer-colored photos of planets, a comet and quasars, a postcard-like shot of a space-shuttle launch) are actually in the museum's collection or just included thematically. All ages. (September)