Here's another excellent offering in Bernard Lee DeLeo's Cold Blooded series. Nick and his crew take on many new adventures in this volume, including a gang of vicious muggers, a Ripper-style serial killer, and an ISIS "training camp."
In addition, Nick must deal with unruly (and deadly) flag protesters with bombs, hit men on his doorstep, pimps with murder on their minds, and an FBI agent bent on revenge.
The book has many, many errors, mostly punctuation but with a few gems such as "did an admiral job"; "had to make due with"; "Nick poured over databases"; and "deep base voice."
I do not know if there will be a Book V, but I have thoroughly enjoyed this series and would be happy if it continued.