The novels largely take place on board Starbase 47, also known as “Vanguard”, which serves as a support facility for a supposed colonisation push by the United Federation of Planets into an interstellar expanse called “The Taurus Reach”. While the station does in fact help colonies across the area, its true mission (known only to a few people) is to study a mystery that began with the discovery of genetically engineered DNA millions of times more complex than any previously encountered, known as “The Taurus Meta-Genome”.

In its effort to understand the Meta-Genome, Starbase 47 has three vessels permanently assigned to it, the Constitution-Class cruiser USS Endeavour , the tiny Archer-Class USS Sagittarius, and the Starfleet Corps of Engineers starship USS Lovell. Another starship, the USS Bombay, was destroyed during the events of Harbinger. In addition to the mission, those who know of Vanguard’s true nature must also prevent others from becoming aware of the situation, especially the Klingon Empire and the Tholian Assembly, both of whom have interests in the region and are suspicious of the Federation’s presence.

While the majority of the characters featured in the first three novels are unique to this series, the Vulcan Lieutenant Commander T’Prynn appeared in two other Star Trek novels, the Lost Era’s The Art Of The Impossible by Keith R.A. DeCandido, and Deep Space Nine’s Lesser Evil by Robert Simpson (and was also mentioned in Unity by S.D Perry). In addition, Petty Officer Razka (from the third novel, Reap The Whirlwind) first appears in the Next Generation novel A Time To Kill by David Mack, and Carol Marcus from Star Trek II: The Wrath Of Khan appears at the end of the same novel.
—Star Trek: Vanguard on wikipedia