Just to give you an idea how whacky this series could get, the final books, High Noon at Midnight (1988), Since Noon Yesterday (1989) and The Ninth of Never (unpublished) take place with Ed (now an old man) facing an alien invasion, which may be only a figment of his tired and shell-shocked imagination. Avallone's son, David, a film maker, who adapted the books into a web serial, describes the conclusion of the series as "A mystery science fiction adventure serial about fathers and sons, the past and the future, sanity and flying saucers. And cockroach headed guys from outer space with ray guns."
I hope we can get more of his books. He does sound like a really interesting character.
Thanks for all the added info, Dr. Drib and Indigo.