Fiction book about British murderer who slows his own heartbeat to be declared dead and escape jail/hospital

i’m trying to remember this book that i was reading in 2024 but didn’t get very far..

-> fiction, NOT part of a series, bought in 2024, paperback, i want to say the cover was a red and black design

-> the story starts with a serial killer (who is the narrator) who eventually is caught. he writes a lot during his time in solitary captivity at the very bottom of a british jail (i think?) and he winds up slowing his own heartbeat down to be declared dead (and is pretty “twisted” about the entire situation to put it lightly). i recall him reading newspaper slips about his own capture while he was in jail, too. after being taken to the hospital, he kills one of the medical examiners (who he talks about being a young man that’s his type of victim) and dresses as him to escape the hospital. he manages to make it out and drive this guy’s car away.

-> i believe he meets someone that plays an important role in the book later on but i didn’t get that far, i just know it rings a bell from the back of the book.