John Christopher 
Lotus Caves 

Two boys discover a series of caverns underneath their moon colony home in this futuristic story from the author of the Tripods series.Marty and Steve may live on the moon, but that doesnt mean they dont want to get away every once in a while. So when Steve makes the suggestion to skip school and take a lunar car out to explore the moons surface like real astronauts, Marty thinks its a great idea. But the fun quickly ends when the lunar car crashes, stranding Marty and Steve beneath the moons surface. There, in a bizarre, cave, Marty and Steve find the unexpected: a world filled with various plants, food, and lifeincluding a man who supposedly went missing more than one hundred years before. The boys think that theyve found the most wonderful place in the galaxybut they soon learn that the joy comes with a price. The strange creature that is keeping them alive also wants to control them, and when Marty and Steve decide that they want to leave, the creature might have something else in mind.