Kids who build something that works.

The books are written to an independent reader of ten or eleven. The younger reader reaches up; the older reader is carried by the plot and the arithmetic. Nothing is named as a principle in the story. A reader closes the book knowing how to notice a need, test whether it is real, make an honest offer, share the work fairly, and take care of what the venture earns.

Chapter titles are plain nouns: The Wagon, Six Customers, The Coffee Can. Every book carries a page from the crew’s ledger, in real handwriting with real sums, so a reader can check the numbers.

For a parent who has read the fables, each book maps to one rung of the system. The mapping lives in the back matter, never in the story.