Axis by Robert Charles Wilson
In this outstanding sequel to Wilson's Hugo-winning Spin (2005), we are taken to the mysterious planet Equatoria, a world apparently engineered for humanity by the inscrutable machine intelligences known as the Hypotheticals. Turk Findley, a man with a criminal past, runs an aeronautical charter service on the newly settled planet. Lise Adams, who hires Turk, is a would-be journalist searching for her vanished father, a scientist obsessed with the Hypotheticals and their illegal life extension technology. Meanwhile, young Isaac, genetically manipulated by rogue scientists so that he may become a conduit between humanity and the AIs, is coming of age, and something enormous and unknown is assembling itself far underground. The various science and thriller plot elements are successful, but this is first and foremost a novel of character. Turk and Lise, who might well be played by Bogart and Bacall, are powerfully drawn protagonists, and their strong presence in the novel makes the wonders provided all the more satisfying. Those unfamiliar with Spin may flounder a bit, but Wilson's fans will be ecstatic.
Axis takes place on the new planet introduced at the end of Spin, a world the Hypotheticals engineered to support human life and connected to Earth by way of the Arch that towers hundreds of miles over the Indian Ocean. Humans are colonizing this new world — and, predictably, fiercely exploiting its resources, chiefly large deposits of oil in the western deserts of the continent of Equatoria.
Lise Adams is a young woman attempting to uncover the mystery of her father's disappearance ten years earlier. Turk Findley is an ex-sailor and sometimes-drifter. They come together when showers of cometary dust seed the planet with tiny remnant Hypothetical machines. Soon, this seemingly hospitable world becomes very alien, as the nature of time is once again twisted by entities unknown.
A quasi-religious group of Fourths from Earth, led by Dr. Avram Dvali, lives in the desert seeded by falling dust. They've created a child they call Isaac with a Martian upgrade (fatal to adults) that connects him with the Hypotheticals. The Fourth-hunting "Department of Genomic Security" is searching for this group or for a visiting Martian Fourth who disapproves of Isaac's creation.