Carnival of the Mind - E. M. Peterson - Bog

Matthew is beginning to suspect the mind he's trapped inside is not his own.
Waking up in a barren wasteland with no memories would be bad enough, but when crashing waves suddenly turn the desert into an ocean, something is obviously more than a little wrong. Confronted with this impossible landscape, Matthew must find a way not just to survive, but to figure out the nature of the reality he's trapped in. Only then will he have any hope of escaping.
A young woman named June tracks him down and guides him through the dreamscape of the Carnival, a land where any story is possible if you are willing to tell it. But June has motives all her own, and Matthew must determine whether he can trust her, or if she is just another force attempting to lock him inside a constructed world.