Nils is a wonderful and thoughtful host, and while his place is quite modest, I was happy with the location, atmosphere and facilities. The guest room is in the attic of an 18th century building, and being Paris, the image of an artist's loft sprang to mind, but it's a lot more accommodating than a classic 'garret'. At the moment, the stairway to the loft is more like a ladder, so that might be a constraint for some.
For good value on a room close to the Bastille, I think this was a good choice for me. Nils is renovating this historic apartment himself, and I was happy to contribute to his construction costs by renting the room for a few nights.