I have a book with a sticker on the flyleaf. It isn't obscuring any text (the only text is the book's title anyway). I'm pretty sure it's postable? I'd like confirmation from someone who knows the rules better than I do :)

that should be ok, it isn't on a text page and I know writing is ok on flyleafs, so I would imagine that a sticker would be fine too

I think it sounds just fine. I know I have received at least one or two books from here that have stickers and it is no biggie.

Thanks!