Farm voices, fish, and a river of grass

''Look Who's Talking! On the Farm" is as clever and happy an introduction to the world of farm animals as one might devise. Babies, toddlers, and pre-schoolers will delight in lifting the book's flaps and ''flapping their lips," as each full-color page unfolds to what seems giant size, encouraging them to imitate the sounds of rooster, horse, cow, sheep, and pig in turn. Each page features a die-cut hole for the animal's mouth -- a simple enough device, but wonderfully effective in making the noise making seem more alive. The book's pages are sturdier than average, so some publishing genius must have noticed that little readers tear the life out of most lift-the-flap books. They won't on this one.

Author Danny Tepper's rhymes are jolly, if predictable: ''There's a cow./Chew, chew, chew./ Cows make milk --/That's what they do./When cows see grass, they" -- well, you can probably guess what sound cows make. The thing here, really, is the overall design of the book and its slapdash, gleeful, elemental illustrations by Valeria Petrone, each cartoony animal painted with surprisingly human expressions, especially around the eyes. ''Look Who's Talking! On the Farm" encourages lively, full-fledged interaction.

Children's-book publishers have been pushing the envelope on nonfiction books for the very young, breaking old rules and creating a rich new approach to real-life material. ''About Fish: A Guide for Children" has the meticulous, botanical-art-style watercolors one associates with the great wildlife artists. Such artistic sophistication is generally reserved for adults, while children get only cartoons. (Some cartoons are nice, too -- see above.)

How lovely, then, to combine Cathryn Sill's crystal-clear prose -- no more than one line to a page -- with her husband's exquisitely detailed paintings. One doesn't need a word more, and Ms. Sill chooses well. I learned, for instance, that ''most fish eat meat" and that ''fish keep growing as long as they live." (Would this were true of humans, too!)