Far From the Tree by Robin Benway

This book won the National Book Award for Young Adult fiction, and I thought it was spot on.  Much like when I read The Fault in Our Stars, I was crying through the last bit of it. That may not be much of a recommendation to some, but what it means is that the book is beautiful and compelling, on top of evoking emotions.
The central theme is what is family?  Is is blood, is it a choice, or is it something combining or containing those elements.  Grace grows up as an only child who has been adopted into a wonderful family.  But she is also the middle child of a threesome who were given up for adoption by their mother.  She doesn't know her siblings, but after she gets pregnant herself at sixteen and gives up her baby for adoption she is drawn to finding them.  Joaquin, the eldest, has been in foster care since they parted ways, and has only just been in a family who love him and want to adopt him, even though he is about to be eighteen.  Maya, the youngest, is in a family with another child, conceived soon after Maya was adopted.  They all have challenges and good things, and the book is about how they find family and support.  Really good, even if you have aged out of the Young Adult target audience age range.