Here are some books that I would recommend for young kids to learn about the Catholic faith:
The “Catholic Treasurebox” series. This is a series of 20 books for Catholic kids. I believe they were originally published in the 1940s or 1950s, but they have been reprinted more recently. You may be able to buy just the first book, or just the first five books, to see if you like them (and if your toddler likes them). My 13-year-old recently saw one of those books on our shelf, and it brought back fond memories for both of us, of me reading it to him and his brothers when they were little.
Any of several books by Tomie DePaola. He has written a number of secular books that are good for kids (like Strega Nona), but he also has written excellent books about Jesus, Mary, St. Patrick, and St. Francis of Assisi.
Any of several good children’s Bibles, with nice pictures and simplified versions of stories from the Bible
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