Which really doesn't make any sense, because otherwise Decker would have been completely unable to relieve Spock in "The Doomsday Machine," nor would Spock turning command over to Scotty in "Journey to Babel" have been an option. But Doctor's Orders is so great, and so much fun, that I'm more than willing to chalk it up to dramatic license.Oh, I haven't read the book yet, so I didn't realize that Spock and Scotty were still around. I guess since Kirk put him in command on purpose, they must have decided to leave him in command.
No, that would've been pretty irresponsible in a crisis situation. The premise of the book was that they couldn't relieve him, that only Kirk had the authority to do that because it had been his order that had put McCoy in charge to begin with.