First off, this has absolutely nothing to do with last year's film Death Sentence with Kevin Bacon. Sure, the titles are the same, and the movie was supposedly "based on the novel by Brian Garfield," but trust me, they have nothing to do with each other. Not a single plot point from the novel found its way into the film. Not even the characters' names are the same.
Brian Garfield wrote this after the film version of his novel Death Wish was released, and while it's not a novelization of Death Wish 2 or anything, at times it sort of feels that way. By which I mean, there is almost no reason for this book to exist, except that the novel Death Wish was adapted into a popular film, and Garfield clearly felt the need to capitalize on it. (Just to be clear, though, this book was published in 1975, years before any of the original film's sequels were released.)
Death Wish the film ended with the main character moving to Chicago. The book did not. However, Garfield chose to pick up where the film left off by moving Paul Benjamin to Chicago. Right off the bat this is sort of strange, since a major theme in the first novel was Benjamin's love of New York, despite what it had become in the '70s, and his refusal to quit the city of his birth. Also, Death Sentence could really take place in any large city. Except for street names, a few buildings, and constant mentions of "the Loop," there is nothing particularly "Chicago" about this tale, at least that I could discern. Also, one thing that I thought worked really well in Death Wish were all the minute, quotidian details of Benjamin's professional life as an accountant, especially since they contrasted so strongly with his nighttime hobby of killing junkies, thieves, and muggers with a .32 revolver. As juxtapositions go, it's nothing spectacular, but it worked, I thought. In Death Sentence, however, this aspect has been largely jettisoned.* For the most part, this book is concerned with Benjamin's activities as a vigilante, his growing romantic relationship with a female attorney who works for the D.A.'s office, and the possible existence of another vigilante on the streets of Chicago; someone who was inspired by Benjamin's "crusade."
Death Sentence also features an aged professor of law named Harry Chisum, through whom Garfield frequently commits the unpardonable sin of authorial intrusion. Chisum has a lot to say about law and order, but most of his ideas are pretty half-baked and simplistic.
In fact, the whole novel is pretty half-baked. It's OK to raise questions about crime that may have no answers, but doing so in the form of a pulp novel that has flat, uninteresting characters and plodding action is really just a big waste of time. After reading Death Wish and Death Sentence I really had no idea what Garfield was trying to say about crime, revenge, and vigilantism, and frankly, didn't really care.
*One detail that the original film changed that I thought worked really well was Benjamin's/Kersey's profession; from C.P.A. to architect. The idea of someone who's intrinsically connected to the character of a city--especially one who designs the large public housing projects that often breed crime--taking his revenge on the populace of a city for their criminal acts is potentially really interesting. There are points in Death Sentence where it seems as if Garfield is hinting at this, particularly when he describes the architecture of the ghettoes in which Benjamin stalks his prey, but it never really comes to anything, since Benjamin is an accountant, as he was in the first novel.