The DVD I received from Corte Ingles includes a trailer for "Boda de Sangre" (Lorca) and this film is similar in spirit, but with even greater tension. This story is reminiscent of Cela's "Familia Duarte", and indeed the DVD includes a trailer to Cela's "Colmena" also, though I haven't seen that film.
I agree with the strong evaluations and comments of other viewers. I'll add that I enjoyed the handling of time in the film, through intermittent flashbacks and juxtapositions of modern elements - e.g., the automobiles driven by the landowners - with the nearly stone-age level of the protagonist family.
Yet for me, the level of dramatic tension became, frankly, too great to bear. I don't know how I could have handled it in a theater. Given I had mouse control, I interrupted it a few times for relief. Then, about two-thirds through, I forwarded the film to see the end. There are occasions when social realism can produce a tale of social horror harder to watch and bear than anything Hollywood's chainsaw boys ever dreamed of.
The acting and cinematography are excellent. I can imagine viewers trying to laugh at Azarias' (Francisco Rabal) rustic charm. His performance is unforgettable - especially as he, like a hand of fate (azar) delivers the much-needed catharsis near the end - but I, and I presume most, will surely view him as a charming and touching victim, fleeing reality to the extent his old age permits - until a certain cruel act drives him to action.
I would have preferred a balancing of the harshness of this film with more moments of beauty to serve as relief, as in the French Manon (e.g., Jean de Florette) films. But here, the actual social conditions were far harsher - "epoca negra" stuff at its worst - and I presume that to add such relief would have been untrue to history. For me, Familia Duarte and Boda de Sangre sufficed.
I will conclude in recommending some of Delibes' recent works. He has a wonderful sense of humor and a great versatility of style that enables him to relate even everyday events in the most charming and entertaining way. It's hard to believe that the same man who wrote Santos Inocentes also wrote "Diario de un Jubilado" and "Mis Amigas las Truchas" or "Las Perdices de Domingo". And hard to believe how far Spain and Europe have come.