I was wondering the same thing the other day. But because I am in Dragonspyre and a Master now, I don't think you EVER go in it, not even for books. I think it is just a prop, an extra place. It is just as irrelevant to any quest as the buildings on the sides of the roads in Wizard City. You can't go in most of those, either.
That is, unless I'm mistaken. It could be for a Spell Quest...
I seriously have no idea why its there. I got no quest when i completed marleybone. It might be there for future expansions or they just thought it would fit right into the Marleybone theme as a cute little area.
