You can't possibly get more central in Madrid than this apartment. Still it's quiet enough for a good sleep as it's located under the roof. The only small drawback is that there is no real view from the windows. I found it convenient that you can pick up the key at the reception of the hostel in the same building upon arrival. There's a fast WiFi connection as well.
Pablo answers very quickly and is providing straight forward and useful information for your stay.
I can definitely recommend this apartment.