A book to finally enjoy a thriller

Hi everyone, I need a suggestion for a thriller book. I want to find that book that would make me enjoy this style. I'm 34M and mainly into fantasy. I almost finished and absolutly loved The first Law and The age of Madness by Joe Abercrombie so I'm looking for something gritty and dark and I especially love flawed caracters. While it's not what I'm into, I am not bothered by gore, violence or anything. Thanks all