I had a great stay in this apartment. The location is really ideal, being only a 15 minute walk from my work in the 2nd Arrondissement. It was also a nice neighbourhood, being close to the Gare du Nord but far enough away from the more seedy districts of that area. There is a lovely square nearby, as well as a local bakery and plenty of options for food. It is definitely small, but it does contain everything that you could need from a stay (kitchen, bathroom, TV).
The only issues to note - be prepared if you're going during a heatwave or in mid-summer. The room is on the 5th floor without a fan or air conditioning, and directly faces the afternoon sun, so it is particularly badly affected. Also, just to note if you're afraid of heights, at the time of writing there isn't anything to prevent you from falling off the mezzanine bed (and there's quite a big drop to the floor).
But, overall it was a really great stay and I would recommend going here!