The overall series title comes from the main 'pocket universe' featured in the books.

They play in the pocket universe, where the chess pieces are alive.

He returns from the pocket universe with a restored and healthy heart.

The plague's back, I've got a pocket universe following me around, and my father was not what he seemed.

"Are you having a conversation with a pocket universe?"

They cross over to the pocket universe, and fire upon the group, killing Cecil.

One person comes up with the idea of creating their own mass drivers within pocket universes.

Walter fears that the Observers had found this pocket universe and have the child.

The Doctor and his crew uncover a pocket universe inside a small tin can.

Perhaps even expand our pocket universe to greater size and complexity.