I highly recommend minimizing the number of separate notebooks in Evernote, and focusing on using tags to separate your notes, at least as far as GTD is concerned. Theoretically, you could use Evernote for GTD by using only one notebook. The main benefit here is that any item can have any number of tags, but only one notebook. Lets say you need to have a face to face conversation with a co-worker about an issue. You can enter that in Evernote and tag it with @office, and Next Action. Then you can sort on those tags to pull up that information. You could also tag int with the co-workers name, say, Bob, and then you sort on Bob's name and pull up everything you need to talk to Bob about. You can also tag it with a project name if it has to do with, so it would show up in a list of items related to that project, regardless of what context it is in. You couldn't do all of this if you put items in separate folders.