Waiting for Dusk — Nancy Pennick

Read a book. Fall asleep. Meet a boy. Is it real or just a dream? Katie's everyday life suddenly turns exciting when she travels back in time and meets the boy of her dreams. Thinking of nothing else, willing to leave the real world behind, she's determined to find out if it's all a dream or not. Returning again and again, Katie almost has her answers until one day her precious book goes missing.