a must for collectors and a basic instruments for whom, such i am, likes to create some model dioramas inspired by this fantastic saga or something about wargaming. the book contains the history of the colonial marines, the detalied description of their weapons and ships and also the description of the other ships of the saga, such as the nostromo. it talks about the weyland yutani and finally a chapter is for their counterpart, the aliens. a great book, with a lot of ilustrations, it's a pity that there are a few shots (pictures).