The Luster of Lost Things by Sophie Chen Keller

 This is by the author of Little Wonder, which I loved. This one has a similar set-up: a single mom raising a boy with a special gift. In Wonder, the boy was a pianist. In this one, he finds lost things. His motivation is finding out what happened to his father--a pilot whose plane disappeared off radar and was never seen again. The mom in this story owns a magical bakery. One day, the new landlord comes in and tells her he's greatly raising the rent, knowing that she can't afford the higher rent. The next morning, mother and son notice that a magical book that they displayed in their shop had vanished. And that sets off the part of the book I wasn't as crazy about, as the boy tries to find the missing book. It turns out that the book has been taken apart, so he's trying to find all the pages, which takes him all over the city, as his frantic mother worries because she has no idea where he has gone. 

As in Wonder, I loved the relationship between the mother and son. They know that together they can face anything the world throws at them.