Well, first I was going to give you the letter zed, because it's the opposite of alpha, which of course if for Oz. But I gave that to someone else because there's a bit more connection to Z there.

Then I was going to give you the letter T because, hey, tequila in the icon. But I'd already given that away, and it didn't seem fair to double up on it.

I thought about D (for Downunder) but that seemed too cliche. As did Q.

And I realised you've already chosen your letter, because you referred me to some Books. So, B!