That's what they were sold as when I bought mine, which I think I still have around somewhere. Specifically made for "English" three speeds with the Sturmey-Archer geared hubs, although they worked on other bikes, too. The thin metal let you reach into spots unreachable with a conventional wrench, and they're surprisingly strong, accepting a certain amount of light tapping with a hammer when the nut you need to remove is really happy where it is and doesn't want to move.
As for a book, never saw one; you just learned which opening fit which nut/bolt on your bike.