If your want to understand a boutique hotel Suites Viena is a good definition.
The hotel is small, located at a quiet street. There is a school in front of it, but because of the time of the year in Madrid there was no noise nor traffic.
I was provided with a master suite, with 2 big terraces on each side of the room and an excellent way to achieve complete darkness. The room was very comfortable.
On my scale of 1 to 5 (1= Poor; 5=Excellent) the bed and the shower were a 4. The bed was a 4 because of the pillow configuration, one big pillow and a smaller one, I would have preferred standard pillows. The shower is a 4 because it lacks a decent size shelve.
This type of room includes a mini bar with a freezing little box which was convenient.
Room air conditioning is quiet and effective. There are outlets in different places (some are at the floor level in front of the bed) where you can recharge and/or connect your electronics.
Breakfast for Madrid standards is good and not too expensive, however the service at the breakfast area is being operated by a very nice lady and it is convenient because it is fast as well.
There is no gym in the Hotel but they have a special rate at a facility near by.