Abaddon's Gate

An alien artifact working through its program under the clouds of Venus has emerged to build a massive structure outside the orbit of Uranus: a gate that leads into a starless dark. Jim Holden and the crew of the Rocinante are part of a vast flotilla of scientific and military ships going out to examine the artefact. But behind the scenes, a complex plot is unfolding, with the destruction of Holden at its core.

Synopsis from Open Library.