She attended public schools in Perth Amboy, New Jersey, and graduated from the Baldwin School in Philadelphia and Pembroke College before becoming an advertising copywriter.
In 1972, Dilys opened the doors of Murder Ink, America's first bookstore devoted entirely to mysteries. In 1975 Dilys sold the bookstore and began work on Murder Ink, an oversized collection of essays and opinions about mystery fiction. Murder Ink was not the first publication aimed specifically at mystery fans, but Murder Ink immediately became the indispensable companion for the mystery community, which it went far to create. ... In the 1990s Dilys moved to Key West, Florida, and opened another bookstore, Miss Marple's Parlour, where she sold mysteries and orchestrated one-night mystery shows. By then she had already begun a long period reviewing mysteries for Kirkus Reviews, where she eventually passed judgment on hundreds of titles before retiring from Kirkus in 2013.