It's a quick read, even for kids; while long at 149 pages, it's broken up into chapters that are 4-5 pages in length.
The story doesn't really seem to flow all that well at times, I'm inclined to believe it's due more from it being translated from German and maybe the meaning of some words getting changed slightly, but there are also some spots that really make you wonder what's going on. Like pretty much every scene with the kid's coach, Larry. Is he psychic? Is he a creepy stalker? Who knows. Obviously not the reader.
While I was reading, I kept being struck by how manipulative the boys are. They manipulate one of their little sisters into being rowdy so they can get out of being grounded; they manipulate all of the adults in the book, too. I kept trying to remind myself that when I was nine, I was reading Christopher Pike, Michael Crichton, and Robin Cook, so a little bit of underhanded "adult management" isn't really that big of a deal.
Other than that, there are some really cool moments. Diego's mom is also the Gunslinger, the uber-cool persona she uses when fatherless Diego needs a "man-to-man" talk. She comes up with the two best ideas of the book while acting as Gunslinger. I thought it was awesome.
My other favorite scene from the book, which leads into the second worst scene of manipulation by the boys and even a small spot of blackmail, is the preparation for the boys walking into the bank. It actually made me laugh out loud.
Overall this was a good book, it would probably be even better if I were an 8-12 year old boy who was really in to soccer. The overarching lessons of teamwork, persistence, and overcoming adversity are well played (get it, well played) and fit into the story without being preachy. I would like to say, the original German title Felix, der Wirbelwind is way cooler than Diego, the Tornado… but an English title is probably more accessible for English-speaking kids J.