A novel written by Gordon R. Dickson, first released in 1987 by Ace Books.

Three years ago, a race known as the Aalaag came to Earth…and conquered it within a week. They are giant, intelligent, efficient, and technologically thousands of years ahead of humans. Humans are viewed as no more than “beasts” by the Aalaag, who use man to harvest the land for their own purposes. Shane Evert is a human in the Courier-Translator Corps. He is one of the very few humans who can actually speak the Aalaag tongue, and so he is assigned to the First Captain himself—the Aalaag in charge of the entire Earth expedition.

One day, something awakens inside of Shane—something he comes to call the Pilgrim—a manifestation of mankind within himself. He, along with a ragtag resistance group, launch a plan to drive the Aalaag off of Earth forever…a plan Shane knows is destined to fail, since a single Aalaag officer in his battle armor could destroy every military threat on the planet without injuring himself in the slightest.

It’s a very good book. Deeply philosophical, as it delves into the core differences between humans and this alien species—Dickson shows an unusual ability to actually make an alien race seem alien. Most science fiction aliens just end up being talking heads who happen just to be drawn a little differently, but Dickson’s Aalaag truly feel different. You truly feel that they have an entirely different belief system, different ideals, and different motives than humans, immeasurably adding to the book’s allure.

Also of particular note is the concept of the Pilgrim which is explored by the protagonist—a symbol which Shane makes up on the fly, and yet by the end of the book is felt and recognized by every human on the planet. It is an interesting idea, that there is something that every person shares somewhere inside them—deeper than individual wants and needs, deeper even than racial memory—the desire to be free.

The manner in which that desire is awakened, as well as being able to actually understand things from the Aalaag side of things (including why they eventually decide to abandon Earth), all makes for an excellent read.