I usually have a pretty strong stomach when it comes to fiction. In television and movies, I can handle most anything and am not really bothered by violence, gore, or abuse. Because I don't see pictures when I read, this is even more the case with books than with visual media--give me the nasty stuff, I can take it.
Jon Cinch's Finn, however, bothered me. The book is not supremely graphic in its gore, but it does contain multiple murders, one of which includes body dismemberment, and the sexual abuse of both an adult and a child, and something about how these scenes were written stayed with me. So before I say anything else, take that to heart--it's violent, and the violence, for whatever reason, stuck with even my hardened heart.
That being said, it's a hell of a book.
The task Cinch sets for himself is not an easy one. While remaining true to events and characters portrayed in Mark Twain's The Adventures of Huckleberry Finn and The Adventures of Tom Sawyer, Cinch tells the story of Huck's ne'er do well alcoholic father, "Pap" Finn (who even in Cinch's book is never given a first name). Moving back and forth in time, Cinch weaves the threads of Finn's strange and horrific childhood, his early relationship with Mary, Huck's escaped/stolen slave mother, his loss of Huck to the Widow Douglas, Mary's murder, and eventually Finn's own untimely death.
It has been a long time (two decades, perhaps) since I've read Twain's books, so I don't remember all of the details surrounding Pap Finn, but it seems that Cinch works into his narrative explanations for things that go unexplained in Twain's own work, such as the discovery of Pap Finn's body in a whitewashed room with walls covered in bizarre charcoal drawings (these drawings are done by Finn himself as he descends into madness after murdering Mary). What he does not try to do, however, is take on Twain's tone (as Alexandria Ripley did--poorly--in her less successful Gone With the Wind sequel, Scarlett). Perhaps because he doesn't spend much time trying to write the same characters on which Twain focused (Huck in particular), Cinch has no need to imitate Twain's style of writing, and I think the book is better for it.
Cinch writes Pap Finn to be as bigoted, mean, and drunk as Twain's supporting character, but fleshes him out in his own voice, making him a real character with a past and reasons for his horrible actions, rather than just a foil for Huck. This (albeit limited) sympathy for Finn, as well as Cinch's original characters, is the strength of the novel. The places where Cinch overlaps with Twain (Judge Thatcher, Widow Douglas, etc.) are a bit weaker. It seems almost as if Cinch is too careful with these characters, perhaps afraid to upset Twain purists. Tellingly, Tom Sawyer doesn't appear at all, and most of Huck's appearances are at a younger age than when we first meet him in Twain.
Please do not think you'll love Finn if you loved Twain's books. Tom Sawyer and Huck Finn are children's characters, and though their adventures did get a little wild, and even a little political, their stories are nothing like Finn. Cinch's book is almost gothic, the cornerstones of its story are violence, alcoholism, and madness. There are no frolicking adventures here, and what humor there is has a very dark underbelly. Finn is every inch a contemporary adult novel, even if its basis is in children's literature from a previous century. However, it's a very good contemporary novel, and if read as such will likely stay with you in a way most contemporary novels don't. Cinch balances the horrific aspects of his story with just enough hope to keep your turning the pages, and at the end you are left feeling as if it was good that you read that, even if reading it was harder than you'd expected it to be. If you think you have the stomach for it, this is a book I would definitely recommend.