The whole doorknob thing in the US is a mystery to me, doorhandles/levers are so much easier to use.

yeah, the book is something that people hate me having read. I know it wasn't my mistake and I tell them that.

as for door handles, most manufactures use interchangaple knobs so you can buy two and swap. You end up with a useless mechinism (i find you rarely can find a different door that needs the reverse handle)