You can join if you've read the books. Here is a list for your chances.

Read book 11 or all of the books: Absolutely!

Read all but book eleven: sure. I'll fill you in.

Up to book 5: if no other person comes sure

Only book eleven: Sure.

1 book that isn't book 11: Sorry...

No books: HOW did you even find this?

4 books or less: Sorry.