A new adventure by one of the surviving giants of the pulp era (Terraforming Earth, 2001, etc.).
Will, an English professor, is one of four faculty members at a New Mexico college who get together for regular poker games and gab sessions. One night, Derek, an astronomer and physicist, shows his colleagues aerial radar photos of a rock formation under the Sahara sands: stone trilithons looking like huge gates. Intrigued, the friends pool resources to explore this Stonehenge-like structure. Almost as soon as they find it, a large insect-like creature emerges from the gate and captures Lupe, a brilliant anthropologist. The other three enter the gate hoping to rescue her. This takes them on a series of adventures through strange worlds connected by the gates. Eventually, Derek is captured by another of the insect-like creatures, which they now suspect to be robots. Attempting to find him, Will and Ram end up in a world plagued by racial conflict. A luminous birthmark convinces the black inhabitants that Ram is their god Anak, returned from the dead to liberate them. That eventually sets off a civil war, in which much of the planet is devastated by a deadly plague apparently released by the natives, who are immune to it. Just as the plague seems to be finished, Will and Ram discover another trilithon and escape to still another world. Finally they are reunited with Derek and Lupe and begin to learn the secrets of the ancients who built the trilithons.
Low-key but inventive adventure.