For the youngest kids fascinated by trains, make tracks to "Niccolini's Song," a new picture book by Chuck Wilcoxen. This gentle story, illustrated with Mark Buehner's soft, dark-toned paintings, introduces us to Niccolini, a night watchman in the train yard. He's a good listener, but that makes him easily spooked as he walks about in the cool night air. To calm himself, he hums a tune his mother used to sing to him. And soon, the anxious steam engines - so noisy during the day - ask him to sing for them, too. "Niccolini knew that some of the trains were perfectly capable of falling asleep without a lullaby," Wilcoxen writes, but "Niccolini didn't mind.... It cost him nothing to bring comfort." Soon, mothers in town bring their crying babies down to the train yard, too. (Little ones will love finding animals in Buehner's clouds.) Everything about this sweet, gently witty story is just right to capture the attention of children (and parents), and then send them all softly to bed.