Actress Danica McKellar, perhaps still best known for playing Winnie Cooper on The Wonder Years, is also a mathematician. She has written four math books for young people (primarily young girls) over the last several years and recently announced her fifth will come out next year.
While her books to date have focused on math subjects for middle and high school kids, the newest book goes younger. Way younger. Goodnight Numbers, illustrated by Alicia Padrón, will be published by Penguin Random House in March and is for young readers from 2-5 (hey, I could read during part of that range). As with most good literature, the story allows some learning to sneak in about numbers.
Goodnight Numbers will be available through the usual outlets, though personally I doubt it will be quite as nice to look at in electronic versions. Of course, you’re mileage may vary.