Nothing feels quite like reading a good storybook with your child in your lap.
Our family has a few favorite picture books that are so loved, many dog-eared pages have tape on them, grimy finger smudges on them, and everyone (especially mommy) has the words memorized! For us, its Dr. Seuss ABCs and anything by Richard Scarry.
Our children go back to these books again and again because they want the experience of entering the world of the book through the words and pictures, which usually happens when sitting in the lap of a trusted, loving adult in their life.
Books with a good story and pictures can transport our children to another place or time. Books can also give the child a "Hey, that's me!" feeling of familiarity when they experience a story about a child like them or activities they do.
And in the case of second language learning, provide a perfect context to introduce phrases, concepts, and vocabulary that wouldn't otherwise exist in the classroom/home learning setting. Don't underestimate the power of books for language learning, even if they are not in your target language!
However, not all books are created equal when it comes to using them for second-language learning.