Not having read the novel yet, but if it follows the pattern of the series, characters like B'Elanna Torres are bound to be interesting. She's half - Klingon, half - human, which often leads to internal conflicts that can be explored further in the novel. Also, Neelix, the Talaxian, with his cheery but sometimes over - enthusiastic personality, could bring some light - hearted moments as well as some deeper emotional arcs if the novel delves into his past or his relationships with the other crew members.
Since I haven't read the new Star Trek Voyager novel, it's hard to say for certain. However, in the Voyager universe, characters like Chakotay can be quite fascinating. He has his own cultural background which often plays into the crew's adventures. If he's in the novel, we might see more of his spiritual side and how it helps or hinders the crew. And then there's the Doctor, a holographic character with a lot of personality. His quest for more human - like experiences could be a great plot point in the novel.