Golden & Grey (an Unremarkable Boy and a Rather Remarkable Ghost) - Louise Arnold

Tom Golden is a boy who doesn't fit in.
Grey Arthur is a ghost who can't figure out where he belongs. When a trick of fate creates an instant connection between them, Grey Arthur discovers what he is meant to be: Tom's invisible friend!
It seems like such a good idea -- Grey Arthur can make sure Tom always has his homework in class and protect him from bullies, and Tom never has to know. But when an accident gives Tom the ability to see and communicate with the ghost world, chaos breaks loose. Now everyone wants a piece of Tom, and Grey Arthur is the only one who can help him!