Tie-in books often get to tackle things the shows they are based on do not. Sometimes it's things that would need too many special effects; sometimes it's letting the X-Men visit the Star Trek universe. In the case of Q-in-Law, it's letting two giant guest star characters meet. Like the epic meeting between Q, who is arrogant and omnipotent, and Lwaxana Troi, who is pretty much the same.