Usually I just get books from the library or yard sales, to save money. But I read this one to the kids and had to buy it from amazon, for our own.
https://www.amazon.com/Other-Side-Ja.../dp/0399231161
Having 3 black and 3 white dcgs, I found it wonderful. The kids and I had an amazing discussion through lunch about it. I'm also taking a 2 part class on diversity in your dc and how we can present it, explore it, talk with the kids about it. So it fits in beautifully. I love when kids ask things so freely and 'just say it', much more so than adults do. It seems like we're always afraid of stepping on somebody's toes. One of my adopted dcgs, who's black, noticed one day that the dad of one of my other black dcgs, was black too. She pipes right up at pick up time and says 'Hey! You're black like me!' She loves it because our town, aside from the local high schools' dorm programs, the majority is white. It is changing, but slowly.