This one goes back to March 1, 2007, when the UK version of World Book Day held an online poll asking respondents to list their "top 10 books they couldn't live without". They got 2000 responses, and the Guardian wrote up an article listing the top 100 books that resulted.
Fast-forward to February 2009. Some wag on Facebook posts the following provocative message:
‘The BBC believes the majority of people will have only read 6 of the 100 books here.
Go to your profile, choose notes, post a new note – copy and edit.
Instructions: Look at the list and put an ‘x’ after those you have read.’
And follows it with the list from the World Book Day poll. Why the BBC? Why 6 books? Undoubtedly to provoke outrage over the idea that those bastards at the Beeb think we're all a bunch of unlettered yahoos.* "I'll show them," the reader says to himself. "Only six books indeed. Humph!" And thus an internet meme is born.
In the current iteration of the meme, instead of simply marking an x after those books one has read, one bolds the books/series one has finished, italicizes the books/series one has started but not finished.
I've got a feeling this meme is going to continue popping up from time to time, like a case of online literary herpes.
*Veiled literary reference.