UNDERGROUND KINGDOM

An extended version of a Choose Your Own Adventure episode from 1983 features more possible endings, color illustrations and melodramatic sound effects.

The scenario opens at the top of Greenland’s Bottomless Crevasse and branches variously through a fall (or a controlled descent) to the Earth’s hollowed-out core where “you” explore, meeting primitive residents, exotic creatures or wild beasts and escaping—or, more often, not. Along with tap-activated groans or roars, figures in the elaborately detailed illustrations often drift about on their own or in response to tilting. The original’s text (and its available Spanish option) has been built up by extending the number of “your” possible fates to 23. A “Book Map” is accessible with a toggle from any screen and becomes visible piecemeal as each plot choice is selected. This handily allows readers both to keep a tally of endings reached and to get back quickly to previous points where the plotline branches. It’s definitely an upgrade from the print edition, and it’s much easier to navigate than previous attempts to carry the series over the digital divide. A nifty digital exploitation of a tried-and-true franchise. (iPad book app. 7-10)