It's a good book -- and you're right, it could never happen today (it probably couldn't have happened then, but at least it was more plausible). The stories were originally published in Boy's Life, and clearly have a Scouting angle.
Other good books for kids on the same theme (kids' almost plausible adventures) are any of the Swallows and Amazons books by Arthur Ransome -- a series by a former Royal Navy captain and Anglican priest named Philip Turner, starting with Colonel Sheperton's Clock -- and A Swarm in May, Chorister's Cake and sequels by William Mayne. Mayne is better known for his English fantasy books like Earthfasts, but this is a realistic series about boys in a church choir growing up in a small English town.
Good stuff.
My 2nd grader loves the mad scientist club books, he’s reread them several times - I highly recommend them too (and they’re still in print)!
Just the idea of kids playing games outside without adult direction seems so foreign to many nowadays. There’s children that won’t come over on a “play date” if you don’t have X-box or Wii!