Corran Horn is a human male from Corellia, a former investigator with the Corellian Security Force who joined Rogue Squadron as Rogue Nine. He was created by Michael A. Stackpole and reached novel readers in X-Wing: Rogue Squadron (Bantam Spectra, 1996); the character had already appeared in Dark Horse's X-Wing Rogue Squadron comics, which Stackpole also wrote.
The cop in the cockpit
Corran's distinguishing feature is method. He does not intuit his way to answers; he investigates them. Stackpole's plots are structured like procedurals — surveillance, informants, cover identities, an infiltration of Imperial-held Coruscant — and Corran is the reason they hold together. He is also, deliberately, a bit of a prig, which makes him unusually easy to write friction for.
I, Jedi
Stackpole's I, Jedi (Bantam Spectra, 1998) is the single most unusual novel on the Legends shelf: a first-person Star Wars book, narrated by Corran, running in parallel with the events of the Jedi Academy trilogy and quietly arguing with them. It is the book people press on you when you say you have read enough EU.
Legends only
Corran Horn has no current-canon counterpart. Rogue Squadron exists in canon; its Legends roster largely does not. Note also that his heritage — grandson of the Jedi Nejaa Halcyon — belongs to a Legends Jedi lineage that current continuity has never adopted.
Reading note
Read the first four X-Wing novels, then I, Jedi. In that order the ending of I, Jedi actually costs something.