Bilingual books are a useful tool for learning a second language. When you show the same story depicted with one image but two sets of words, the young minds learn to describe the same situation in two different tongues, learning the words and meanings side by side. This also broadens the understanding of the conceptualization of actions, going beyond the literal translation of the words.
By knowing a story in two languages, children also acquire the understanding that the same idea or event can be described in more than one way, and that some ideas are portrayed differently in other languages or cultures. This wider learning filter of the bilingual or multilingual mind is therefore much more prepared for a globalized world than a one-language mentality.