I honestly think it only got good reviews because it's about slavery and was written by a black person. Like they weren't evaluating the actual writing, just the subject matter. There's great slave narratives and novels, this isn't one of them.
It also just as a whole seemed like a dumbed down Toni Morrison rip off. The book was written to appeal more as a thriller or a "page-turner" than an actual literary work. Like he was writing it for a movie adaption.
For a novel called "The Underground Railroad" the entire thing is basically gimmick that doesn't work. Because the entire premise of the novel is that there's an actual, physical Underground Railroad. But this Underground Railroad appears on maybe 5 pages put of 300+.
Nearly every male character was completely interchangeable.