Michael Jan Friedman 
My Brother’s Keeper: Enterprise [EPUB ebook] 

The gripping conclusion to the story of Jim Kirk’s lost friend, the man who helped shape a Starfleet captain…. Captain Kirk has returned to Earth to attend the funeral of Gary Mitchell — the man he was forced to kill. As he wonders what he can possibly say in eulogy, he thinks back to the first time he had to do without his friend, several months earlier…. Kirk has just taken command of the U.S.S. Enterprise and brought along Gary as navigator. Kirk has learned to depend on his friend’s good sense and advice, but when Kirk confronts the Klingons for the first time in his career, Gary is taken captive and cut off from Kirk. Now the young captain has no choice but to rely on a man he barely knows, a Vulcan named Spock.