As an avid true crime reader, I give most books a chance surrounding this subject. While this book wasn't a GREAT read, it was interesting enough to make me want to finish it. As most have already stated, Dead Men Walking is a fairly speedy read, and flows quite easily. And as others have pointed out, the authors opinions do shine through the chapters quite prominently, and I do believe at the start of the book, it gives the impression that it is up the reader to make up their own mind about the criminals. That is not to say that I do not agree that most (if not all) of these crimes are disgusting, I think the author should have perhaps eased off his own opinions and allowed the facts to speak for themselves.
All in all, I'd say give the book a go, but don't expect it go too in-depth about the individual crimes, as it packs in quite a few criminals. If you're looking for focus on the crimes committed, I'd say look elsewhere. But that's just my opinion!