Aliens is a novelization of the film of the same name. The novel was written by Alan Dean Foster. It was published in June, 1986.
Publisher's summary[]
Now there's a Whole Planet of Them, Waiting...
Ripley is going back...the sole survivor of the terror that struck her space comrades years ago, she now steels herself to help lead an expedition to the hell she once escaped.
For on a planet far from Earth, alien beings swarm, hungry for the human face, ready to make the human race their nesting ground. Here waits the ultimate nightmare of Alien, hundreds of times stronger, more insidious, and practically invincible.
Here Ripley must re-enter a world of sudden, unspeakable horror...one that attacks without warning again and again and again.