I have no interest in this. Alien is way too violent for my delicate as a flower constitution. It might not so much be the case if it were offset by more actual "scifi" and not just a scifi-themed snuff film series.
That being said, I'm glad he's doing this since it puts him just one more project away from the proposed Bladerunner sequel/reboot/whatever, which I hope he doesn't live long enough to make.
I don't want to spoil anything, but despite what you've seen/heard (trailers), the Alien prequel is a melodrama that centers on Newt's (Aliens) great-great-grandparents and their toils harvesting sorghum on a farming planet that is, essentially, a latter-day "company town" writ large (across several planets and planetoids).
Note: other commentators on the 'net have argued that the farming planet is more akin to the feudal manor system, but Ridley Scott himself has dismissed this assertion as, in his words, "mere poppycock."
Apparently, major conflict arises when Newt's great-great-grandfather proposes to introduce cassava into the sorghum/rye/soybean crop rotation. In order to accomplish this, he intends to drop sorghum from the crop rotation cycle, much to the horror of his family.
As it turns out, he has made a breakthrough in hydroponics that would allow him to increase the starch content of legumes and vegetables by ten-fold, but the cultural and societal reverence for sorghum (it is revered as the cradle of life in this society, apparently) prevent farmers from experimenting with different crops. Indeed, "Give me Sorghum or give me Death" is a mantra in most farming communities established by a *certain* inter-galactic mega-conglomerate that dabbles in military contracts when opportunity strikes.
Ridley Scott consulted with experts in hydroponics, agriculture, irrigation, fallow fields, manors, grist-mills, etc. to make sure the sci-fi was firmly rooted in plausible science.
When a virus decimates the non-native pig/boar population (introduced by the settler-farmers), Newt's great-great-grandmother is driven to near-suicide (her beloved pig "Quahog" being the only means of harvesting truffles). It is in a moment of desperation, however, that she discovers an enormous spacecraft buried under a substantial truffle patch near the sorghum fields. In Ridley's own words, she is "torn between the immediate crises facing her family (sorghum vs. cassava, utter collapse of truffle production) and the allure of an alien ship undisturbed for millennia beneath fallow fields."