Domu'e Luna is a rare surviving example--and an excellent one--of the kind of informal establishment that used to be common in every Italian town: a place to stay that was larger than a bed-and-breakfast but not quite a hotel, typically having accommodation for a dozen or so guests. At their best they were very good indeed: cheaper, more welcoming and often more comfortable than the "commercial" establishments. This one is worth going out of your way for.
The greatest challenge is finding the place. It is not signposted from the main autostrada (SS 131). The best way there is to follow the signs for Villanovaforru; Lunametrona is 5 km further on. Once in Lunametrona, which is not large, you'll find that no one has ever heard of Domu'e Luna or Via Gioberti, the small street on the edge of town in which it's located. Instead, ask for directions to the Scuola Materna (pre-school). Keeping the school on your right, after 100 m or so you'll see the road fork gently rightwards. Domu'e Luna (which itself bears no sign or other identifying marks) is the large villa-like house plainly visible at the end of this right-hand fork.
Like most of Sardinia, the property is a step back in time. The en-suite rooms are furnished in classical Italian rural style: simple, tasteful and comfortable. The breakfast is immense. There is a spacious terrace where you may sit and pass the time with the house's three good-natured cats. Other than that, Domu'e Luna is a refuge from modernity. Your room has neither telephone nor television; the nearest internet connection is in Oristano or Cagliari, each about 60 km away. With the exception of some plain but good eating houses, a small cinema and a couple of bars, nightlife in Lunametrona is nonexistent. However, nobody in their senses would go there in search of stimulation. This is a place for people who do not need constantly to be diverted, and who wish to rediscover the traditional meaning of relaxation.
I agree with what others have said about the proprietors, who are courteous and considerate. If you require help and advice, they are ready to provide it; if you prefer to be left to your own devices, they know how to do that too. For those who want a reminder of what Italy used to be like before it turned into a Mediterranean-tinged version of everywhere else in Europe, this is a good place to find it.