I'm SURE you all know what a TARDIS is, but just in case there's someone reading who hasn't seen Dr. Who, it was a police box that was basically like a small, free-standing closet sitting on the sidewalk. But when Dr. Who walked into it, we saw that on the inside it was really a multi-levelled time-and-space travelling machine.
And the best books are like that. They look so small and innocuous, but wen you open them up and start reading, they take on extra dimensions and transport you to another time and place.
So do that with your book. Make your book a TARDIS.
What TARDIS-like books have you read lately?