The 26-Story Treehouse (Electronic book text)

Andy and Terry live in a 26-story treehouse. (It used to be 13 stories, but they've expanded.) It has a bumper car rink, a skate ramp, an antigravity chamber, an ice cream parlor with 78 flavors, and the Maze of Doom--a maze so complicated that nobody who has gone in has ever come out again. Well, not yet, anyway.
This time, the two friends have a whole week to finish their next book, and Andy even knows what it should be about--the story of how he and Terry first met. But, life is NEVER boring in the treehouse, and emergency shark operations, giant storms, and wooden pirate heads are just the beginning....