Doctor Proctor's Fart Powder

Nesbo, Jo.  Doctor Proctor's Fart Powder
December 29th 2009 by Aladdin 

Nilly, who is incredibly tiny for a grade school student, moves into a new house near Lisa (who is in his class), and makes the acquaintance of Dr. Proctor, an eccentric scientist who has invented a powder that makes people fart. There's the low grade, average ("totally normal")  fart kind (and the farts don't smell), but then there is the industrial strength stuff that causes Nilly to launch into space and chance bodily injury. Dr. Proctor hasn't been able to sell any of the powder, but Nilly and Lisa have a small business going at their school.  Eventually, the two get some revenge on the evil twins Truls and Trym with the powder, but also save the twon festival by using the powder wisely.
Strengths: I'm sure that there are a huge number of tween boys who would pick this up just because it had fart in the title. The book has some amusement value.
Weaknesses: This is translated from the Norwegian, and has that odd, written-by-author-of-adult-fiction feel to it; it's condescending in many ways, plus goofy in a way that I'm not sure would really resonate with 6th graders in the US. 3rd graders, maybe.

I picked up the first book because the fifth one just came out, and I hadn't read any of the others, which include Bubble in the Bathtub, Doctor Proctor Who Cut the Cheese, The Great Gold Robbery, and Doctor Proctor's Fart Powder: The Magical Fruit (October 29th 2013 by Aladdin.

Please know that I adore Captain Underpants. There's a totally different tone with those-- Pilkey seems to understand kids on their level, not try to guess what they will find funny. These just seemed not quite right for older middle grade readers. Anyone out there have them in a middle school library? How do they fare?