You can't expect Rowling to show her true authorial skills in a four page prequel. Nor can't you expect any life-altering information to be taken from this "Prequel". Unfortunately, it does not add anything to the overall Harry Potter experience and it does not raise many questions. This should not be called a "prequel", but rather a teaser for an actual Prequel that J.K. Rowling said she will never write.
Alas! It is a short action scene lacking any content that would deepen your love for and understanding of James or Sirius. So, get rid of your high expectations. We already know they were bad boys and now we have a scene that demonstrates their - too recognisable for my liking - muggle-like teenage rebellion. "Outsmarting" to muggle police officers. Nothing smart about that, nor very rebellious if you have magic and brooms.
I decided to give it 2.5 stars: two stars because it really is just "ok", but three because it does give us some more information about James and Sirius's friendship. However, I decided not to round my rating up to three stars, because for a narrative framework that is Harry Potter, this scene is a bit too mundane, too mugglish for my liking. Of all the teenage acts of rebellion she could have written for James and Sirius, Rowling went for one with an obvious and predictable outcome.
If you want to read a decent fan fiction about James Potter, I have heard great things about G. Norman Lippert's series: James Potter and the Hall of Elders' Crossing, James Potter and the Curse of the Gate Keeper, James Potter and the Vault of Destinies and James Potter and The Morrigan Web. I have not read these yet, since I fondly object to fan fiction because it is too hard to find anything decently written in the copious amounts of stuff that you can find online. However, this series is amongst the most downloaded ebooks on Goodreads, which is the only reason why you can find Lippert's series on my reading list. So if you decide to follow my suggestion, let me know what you think of the James Potter series.