This French sci-fi thriller consists of three intertwined narrative segments: 1) a fascinating storyline about intelligent ants who think, emote, build cities, and communicate using pheromones; (2) a not-so-interesting story about humans disappearing down a mysterious tunnel whose relationship to the ants is not revealed until the last chapter; and (3) reproductions of a purported encyclopedia called "the Encyclopedia of Relative and Absolute Knowledge," created by one of the human characters.
The "ant" story is by far the most interesting. The ant characters behave like real ants, but have intelligence and personality (though they are given numbers instead of names). The story is told from the perspective of workers, drones, warriors, and even a queen. The ants have some fascinating adventures, all told from an "ant's eye view." The effect is a little bit like the rabbits in Richard Adams' Watership Down: A Novel. But where Adams' rabbits behaved mostly like English country folk, these ants have mysterious and exotic habits and attitudes. They are highly warlike, and their cities bear odd Asian-sounding names. The chambers where their queens live are known as "Forbidden Cities," further strengthening the exotic "Oriental" feel of their society. Werber does a fascinating job of rendering the ants' point of view, their civilization, and the many hazards they face.
The "human" story is not as compelling. It begins with a cliche: a man inherits a strange old house from his uncle. Soon he disappears down a mysterious tunnel in the back of the house built by its previous occupants. He is followed by more and more characters who simply disappear down the tunnel, including firemen and policemen, giving the narrative the feel of a children's book--remember the spider who swallowed a fly? We don't find out what's up with the tunnel until near the end of the book, when its secret hardly seems to have been worth waiting for, and doesn't add much to the "ant" saga. The whole "tunnel" thing seems to have been a set-up for a sequel.
Finally, the Encyclopedia segments are somewhat interesting. The human character who wrote them has some interesting ideas about philosophy and falls in the long French tradition of attempting both to codify knowledge and share philosophical (and sometimes subversive) theories about the world and society. But I think the reader will enjoy the "ant" story best.