I found the first book so quirky and fun that I decided to read the sequel right away.  The series is a grade-schooler's dream: crazy situations, funny dialogue, and a little bathroom humor thrown in for good measure.  (Pretty tame though, in a day when children's books can be called "Captain Underpants.")

This time around Hashbrown is confronted with a rival student who has just come into a lot of money and is building a treehouse to eclipse his own.  (The rival student is the "Mashimoto" from the title, in case you were wondering)  The book does of a great job of building on the previous material and adding its own touches.  In addition, it is quick and well-structured storytelling that I think even adults can enjoy. 

If you haven't already, give this series a read.  I here there is a third helping in the works...