Regulus of Hogwarts: Lord of the Stars

Regulus wandered through the shop and picked up a cauldron fitted with a temperature gauge.

Clever design: temperature-sensing rune-script on the inner wall, with corresponding readouts on the outer surface showing the current heat — no more guessing by experience when brewing potions.

"Like it? Take one." The witch noticed his interest and winked. "Your father won't charge you."

Regulus set the cauldron down, voice tinged with regret. "School doesn't allow it."

"Hogwarts and its rules." The witch shook her head disapprovingly. "My grandson goes there too — writes home complaining every other day."

The third shop was a general store stocking all manner of magical household goods.

Self-sweeping brooms. Boxes that kept food fresh. Weather-forecasting crystal balls. Quills that wrote on their own.

This was the largest and busiest of the three; five or six customers queued at the till.

The shopkeeper, a balding wizard, was ringing up an elderly witch. He spotted Orion and Regulus and gave a quick nod — hands never stopping.