THis inaugurates an extremely ambitious series of scifi novels, which reached six in all. There are many mysterious references that are explained in later volumes, which serve to whet the appetite. Benford maintains a sense of mystery and wonder quite masterfully. In later volumes, it gets deeper and much better.
The plot is that a space pilot, Nigel Walmsley, an iconoclastic Brit. He discovers a remnant of an extremely ancient space vessel, which he disobeys orders to explore. What ensues is a wonderfully enigmatic encounter with an alien intelligence, whose intentions are not clear, though at times it seems menacing. The novel leaves many questions unanswered, in such incidents as a beam of energy that affects the way the Nigel can think, somehow changing the organization of his brain; there is also a signal of a change in the human genome.
The characters are what makes this writing exceptional, even if their sexual predilections (2 f's and one m) are a bit much after a while. Benford is a very good writer, one of the best at hard sci fi, but you do feel at times that he is straining to think up what happens next.