Most of the members of the Dublin Murder Squad are one-dimensional males we barely get to know. There's Tom Costello, the "grizzled veteran" (1.30); Quigley, who is like an Irish version of Quagmire from Family Guy, telling stupid jokes and laughing at himself; and O'Kelly, the classic blustering police chief type.
There are also people who aren't part of the Murder Squad exclusively, but are close enough. Cooper is the snippy forensic pathologist who takes a sick kind of joy in gruesome autopsies, making this colorful character practically written for the big screen. And, just to have equal-opportunity one-dimensional characters, there is Sophie, the crime-scene tech whom Rob is attracted to (because she looks tiny and helpless).
Rob goes out with her in the end, but she breaks up with him saying that she "know[s] the difference between intriguing and f***ed-up" (25.71) and Rob is the latter. That might be one of the smartest things anyone says in this book.