I have found a bookstore and publisher that deals exclusively with books about books. Oak Knoll Books in Delaware. Admittedly, many of these books are so specialized that they have a limited audience, but to discover an entire store given over to books about books makes my heart go pitter pat.
It’s the bookshop that every bibliophile secretly fantasises about, and occasionally encounters in a Jorge Luis Borges story. An entire bookstore full of just books about books. Reader, I’m here to tell you that this is no ficcione: such a dream bookshop exists. You will find it in the historic colonial town of Old New Castle in a three-storeyed Opera House built in 1879 where two floors house, in an almost labyrinthine fashion, shelf upon shelf upon shelf of books on books.
Oak Knoll Books has the largest inventory in the world of books on books. Its publishing imprint, Oak Knoll Press, tops even this Borgesian fantasy by being a fine press devoted exclusively to publishing books about books.
More from Pradeep Sebastian’s gushing article about the store here.
Thanks to Becky at The Book Frog for the link (via library thing).
Nathalie Foy 
I love Oak Knoll. Their publications are, unfortunately, rather expensive, so I’m always thrilled when I find one in a used bookstore at a reasonable price!
Be sure to get on their email list.
Thanks for the tip! I’m having fun exploring their catalogue…