The following are the main characters in the Star Trek: New Frontier series of novels.
Captain Mackenzie Calhoun (born M'k'n'zy of Calhoun) is a member of the Xenexian species, a race that, for years, was under the rule of the Danteri. (Xenexians closely resemble humans, with purple eyes being the major distinguishing feature.) Calhoun led the Xenexian revolution that freed them from the Danteri, a revolution that ended before Calhoun turned 20. After a visit from Stargazer captain Jean-Luc Picard, whom he had seen in a hallucinatory vision prior to the meeting, Calhoun left his homeworld and joined Starfleet. After a falling-out after the events surrounding the death of his captain on the USS Grissom, Calhoun left Starfleet, but was lured back by Picard and took command of the Excalibur. His cowboy-like command style sometimes irks his co-workers (particularly Shelby and Jellico), but he has always been able to get the job done.
Peter David has stated that the character of Commander Quentin Stone from his 1991 TNG novel, A Rock and a Hard Place, unintentionally turned out to be an early draft of Calhoun.
Calhoun is the only non-TV Star Trek character to be the subject of an action figure; the figure comes with a sword, and is highly detailed. James Cawley, who plays Kirk in Star Trek: New Voyages, made a guest appearance in the Star Trek: Hidden Frontier episode "Vigil" (season 6, num. 605) as Mackenzie Calhoun.
Lt. Commander Elizabeth Shelby first appeared in the TNG episodes "The Best of Both Worlds Parts 1 and 2", where she was played by Elizabeth Dennehy. Shelby was assigned to the USS Excalibur some years before New Frontier under the command of Captain Korsmo. She was romantically involved with Calhoun during her time at Starfleet Academy. When the series began, Shelby served as first officer of the Excalibur under Calhoun; their relationship was decidedly platonic, but she has since married Calhoun, been promoted to her own command as captain of the USS Trident and later, Admiral in command of Starfleet's Bravo Station, where she administratively oversees activities in Sector 221-G, the focal point of many New Frontier adventures.