Strange Games. The Multiversal Chronicles, #8

Kitty, Toby, Sam, and Jemima embark on a task for Merlin, jumping into the unknown. But where are they? Why do their surroundings keep changing? Knowing something has gone badly wrong, Lizzie, Luke, Jessica, and two of their friends join them in a weird universe, where they all have to pit their wits against a gamemaster, a gamemistress, and a familiar yet unfamiliar adversary.  How can they escape this bizarre place? Playing the game to its conclusion seems to be the only option.
But how many levels will they have to pass through? And what will actually happen when they finish the final level? There's only one thing they know for certain: the game's on!