There are 5 books in the The Edward X. Delaney series. The newest book is The Fourth Deadly Sin which came out in 1985.

1
The Anderson Tapes

Book cover of The Anderson Tapes
The explosive Edgar Award–winning debut novel—told entirely through surveillance recordings, eyewitness reports, and other “official” documents—by New York Times bestselling author Lawrence Sanders

New York City. Summer 1968.Newly sprung from prison, professional burglar John Anderson is preparing for the biggest heist of his criminal career. The mark is a Manhattan…
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3
The Second Deadly Sin

The Second Deadly Sin
Edward X. Delaney returns in this spellbinding tale of greed, deception, and the brutal killing that shocked New York's art underworld.

4
The Third Deadly Sin

The Third Deadly Sin
Edward X. "Iron Balls" Delaney is called out of retirement by the NYPD to hunt out a random killer at large in midtown New York.

5
The Fourth Deadly Sin

The Fourth Deadly Sin
When saintly New York psychiatrist Simon Ellerbee is murdered, retired Chief of Detectives Edward X. Delaney pursues the murderer on a list of the doctor's six most potentially violent patients, obtained from his beautiful psychologist wife