Great for solo or couple. Love the location - close to parque retiro, the art museums (prado, etc), restaurants and cafes, on pedrstrian street with cute boutique shops (if want the more commercial and/or touristy, Sol area is just a short 5-10 minute stroll from doorstep).
Apartment as described - double bed (very comfy), open plan studio. Wahing machine (and had detergent!) and hair dryer. Wifi. Ticks all the boxes for us.