Manuel's place is great if you're looking to stay in the heart of Malasana for a few days. The building is pretty modest but it's in a great location, very stylishly designed and sparkling clean (like 5 star hotel room clean!)... Manuel is also very communicative and helpful and the App key (rather than a physical one) works very well.
A few things to keep in mind though, it's a studio and while they've made good use of the space, I wouldn't suggest it for more than a few days if you're 2-3 ppl and want to use the space to more than just sleep (remember also there are no doors so you better be with ppl you're comfortable with). It also lacks a bit of natural light (but has lots of artificial ones)... The sound insulation with neighbours isn't the best either (although that goes for most old buildings in Spain) so bring earplugs if you're a light sleeper. But for what I needed, it was perfect! Would definitely stay here again!