Maybe I'm just not a fan of the prison planet genre, but this one does get pretty good in the second half
For a while I thought I was accidentally rereading the author's other prison-on-another-planet book (Cage of Souls) which I just didn't get into and gave up halfway through, but maybe I should have stuck with it, because I also found this one slow-going and uninterestingly written for the first half but then it really got going and I thought the writing was almost poetry in the final chapters. My new theory is he's a different writer once the extraterrestrial biology gets going and the boring human-on-human preliminaries are out of the way.