I would argue that there are two equally strong conflicts in Dean's book Monster.
First, Steve is on trial for being an accomplice to a robbery that turned into a murder. Most of the book centers around his trial and various testimonies. One interesting facet of this conflict is that it is never fully resolved for the reader. Although Steve is found not guilty, the reader is left wondering whether he really did act in conjunction with King, sweeping the store they robbed to make sure no one was inside. Following the verdict, Steve's own attorney stiffens when he tries to hug her, and he is left wondering what she truly sees in him. This external conflict of Steve vs. society is perhaps due to Steve's own actions—and maybe not.
Second, Steve battles internal conflict from the very beginning. In the jail, he doesn't recognize himself in the mirror, metaphorically representing that he doesn't fully recognize the person he's become. Is this because he was actively involved in the murder or because of the way society views him? Five months after the trial concludes, Steve is still struggling with whether his lawyer views him as a "monster," and he is still trying to find some inner peace. Again, his inner conflict is not resolved with the plot's conclusion. There are no easy resolutions to be found with the conflicts in Monster.