One book that I've recently learned about is Letters of Love from China, written from the perspective of the birthmother. It won the 2008 Mom's Choice Silver Award for the Best Children's Book in the Family Life category.
"Written from a birth mom's perspective, Letter of Love from China by Bonnie Cuzzolino, paints a loving and respectful picture of a child's relinquishment in China. Through vivid and colorful illustration, combined with clear, simple language with appeal to all ages, Letter of Love from China has a poignant yet uplifting message. So often parents struggle with positive ways to answer questions about why their child was abandoned in China. This book will help parents answer these questions and communicate the heartfelt and loving choice that a birth mom in China makes, and the cultural context behind this decision. It depicts the relinquishment for what it is, a selfless act of love." Beth Smith, MS Director of Services, China Program, Holt International