Short answers, pulled from the story.
The Star Wars X-wing series was written by Michael A. Stackpole and Aaron Allston. Stackpole wrote the first four novels and the eighth, while Allston wrote novels five through seven, the ninth, and the tenth.
The Star Wars X-wing series consists of ten novels. The first nine were published between 1996 and 1999, and the tenth, Mercy Kill, was released on the 7th of August, 2012.
Wraith Squadron is a starfighter unit created by Wedge Antilles in the fifth X-wing novel, also titled Wraith Squadron, published in 1998. Antilles recruited pilots who were on the verge of being discharged from Starfighter Command, selecting for commando-type skills rather than conventional military standing.
The first seven novels take place six and a half to seven and a half years after the events of the original Star Wars film. Isard's Revenge takes place about two years after that, and Starfighters of Adumar is set three to four years further on. Mercy Kill takes place over three decades after the previous volume.
Corran Horn is the primary new character introduced in the first novel, Rogue Squadron, published in 1996. His arc across the first four books includes capture, imprisonment in the Lusankya facility, escape, and exonerating Tycho Celchu at trial.
Stackpole contacted Zahn before the X-wing series began to coordinate over the shared use of Rogue Squadron. After Rogue Squadron was published, Stackpole asked to use Zahn's character Talon Karrde; Zahn changed about three words of dialogue to accommodate the request. Zahn later asked to borrow Stackpole's character Booster Terrik for the Hand of Thrawn duology, and Stackpole returned the same adjustment.