“Well,” said the inspector, refastening his notebook. "The case seems clear enough.
© Agatha Christie
So, notebook here is just a notebook.
(To me, it always takes some time to switch to that time, despite the fact that in the UK laptops are more commonly used :D)
But refastening in this context?
Anyway, to me it sounds very strange to say fasten a notebook.
What on earth did he do with his notebook? :lol: