The title sums it up. This is a book about greetings around the world and the way simple words can have many meanings. "Hello" is an introduction, a welcome, a spectacular welcome. It can be said in different ways ("good-morning," "howdy" ). It can even be said without words (a wave or the shake of a hand.) It can be loud or soft or take on many moods. The same is true of "good-bye," although that is often more difficult to say than "hello." Using her signature artwork, appealing in its childlike simplicity, Aliki shows in full-page boxes and cartoonlike strips all the many moods of greetings. Occasionally, she stretches the concept a little--"peek-a-boo" is not really a playful "hello," nor do you see many kids in baseball caps saying "toodle-oo" --but children should enjoy the ruminations anyway and perhaps mull over the different feelings these words evoke. Ilene Cooper