A pictorial overview of Alien lifeforms based on actual sightings and reports is compiled in this unusual historical collection from the late 1800’s to the present. Opening with a tongue-in-cheek poke at the plethora of National Audubon Field Guides to flora and fauna, Science writer Patrick Huyghe gathers unusual reports of Alien encounters worldwide for his field guide to extraterrestrials. Fifty very different Aliens are skillfully portrayed in black and white sketches by illustrator Harry Trumbore.

Author Huyghe discusses ambiguities with current classification systems for Aliens which fail to cover variations within groups, such as nonhumanoids. Huyghe objects to systems disregarding highly unusual lifeforms as isolated cases, and instead, devises a system to encompass most anomalies reported.

Huyghe resolves this dilemma by dividing Aliens into four primary classifications: Humanoid, Animalian, Robotic, and Exotic. Within these classifications he develops separate types, and under that, variants.

Humanoids include humanlike beings or Nordics, short grays, short non-grays, giants, and a nonclassic catchall group containing a solid black form, mummylike creatures, as well as a handless being. These creatures are placed with humanoids because they exhibit the same basic body structure as a human.

Animalian classes may be hairy, scaly, move on four legs, or have wings. Animalians include hairy mammalian, reptilian, amphibian, insectoid, and avian.

Robotic creatures have a characteristic mechanical nature to their movements. Robotic Aliens include metallic types looking like tin cans or slabs of metal. Fleshy Robotic types have android characteristics of either humans or animals, such as humanlike arms or legs or scaly skin of a reptile.

Exotic entities represent a catchall group of Aliens which would not be considered humanoid, Animalian, or Robotic. Exotic Aliens include apparitional or physical types. Apparitional types include ghostlike images or nonhumanoid creatures that are only partially formed or appear to exist in another dimension. The physical type is a being in the shape of a blob.