A book in Star Trek Deep Space Nine series.
"On the eve of Bajor’s formal entry into the Federation, First Minister Shakaar is assassinated, derailing the induction and plunging the planet and station Deep Space 9 into chaos. Investigation into the murder revealed the presence of a parasitic conspiracy threatening not only Bajor’s future with the Federation, but the very survival of both."
Note: Elim Garak plays a minor role.