One of the most in-depth looks at ESU ever written. Samuel Katz has several books to his name, including one on LAPD. But this one is strictly about NYPD ESU.
Sadly, it is also a dated book and as a result provides a look into ESU before the attacks of September 11th. Several officers lost on that fateful day are pictured throughout. For anyone interested in NYPD's ESU, or SWAT in general, this is a great reference book to have.
The book goes into the break down of all the individual units, as well as equipment, weapons, etc. .
While LAPD claims the title of the first "SWAT" team, NYPD ESU has been doing it "All" since 1930. As their motto says "Anytime, Baby"