The apartment is in an excellent location–you're steps away from Atocha Station, Madrid's major art museums, the Retiro, and numerous bars and cafés. The space is more than ample for one or two people, with a good sized-bedroom and large closets; a roomy living room/dining room; and a good-sized kitchen. With numerous supermarkets and public markets nearby, it's easy to buy and make food, if you'd like. I felt lucky every morning I was there, and I would gladly rent the place again.
One bit of advice, and one minor complaint, neither of which should detract from my positive review. The advice: make sure you know how the key to the front door and the building work! I had a devil of the time my first two days with the keys, and Maria was kind enough to come help me. The minor complaint: one of the bathrooms does have a bit of a disagreeable odor, as a previous review mentioned. Since the apartment has two bathrooms, this doesn't pose much of an issue.
Again, Maria was a great host, and I'd gladly rent from her again.