The Zen Den is in a very non pretentious Paris neighborhood with lots of good food easily available. The street it is on is not very busy and I found it to be surprisingly quiet for a major cosmopolitan area. The metro is also close by.
Other reviews mention paper thin walls where conversations in the next apartment are easily overheard, but I did not find that to be the case. Fred does provide earplug though.
The room, as you can see from the pictures on Airbnb, is funky and eclectically decorated with real character.