I, too, assume you mean the classic "87th Precinct" books, which inspired "Hill Street Blues," "NYPD Blue," and countless other television shows and novels.
In my view, there's no need to start at the beginning. They each stand on their own.
Happy reading.
Paul Levine
Author of the Jake Lassiter Novels
"Mystery Writing at its very, very best." Larry King -- USA TODAY
"To Speak for the Dead"
"Night Vision"
"False Dawn"
"Reversal"
"Mortal Sin"