The House Inside His Head av David Malsch

Will is a target for bullying. His solution? To build the most magnificent hiding place of all: a house that becomes only greater. The only problem is . . . the house exists only in his head. As the bullying intensifies in his school on an island off the coast of north Florida, so more Will hides. It seems, in fact, he will retreat into his imaginary house forever. But along came a savior named Betty . . .