I'm going to tell you here and now, I'm not sap. I hate the "born in my heart" adoption sentiment (and others). Hallmark and Lifetime movies have me rolling my eyes. Kitties and puppies have pretty much zero effect on my tear ducts (babies are WAY more precious). I very rarely cry.
I carry my non-sappy attitude to choosing adoption books for my kids. Not because it's not ok to have emotions surrounding adoption, but because kids like things that are funny, vibrant, and different. Pastel illustrations do very little for most young children. (Thus why it was SO important to me that my children's books, Black Girls Can and Poems for the Smart, Spunky, and Sensational Black Girl had colorful, fun illustrations.)
Even though all adoption books don't apply to your particular situation (special needs, transracial, sibling group, international, etc.), reading about the different types of adoption can be interesting to kiddos. We have such a large diverse group of friends, may of those children adopted via foster care and international adoption, that my kids love learning about their friends' stories!
So in no particular order, here are our favorite non-sappy adoption books, all available from Amazon: