"The Year of the Intern" was a failure, but Cook began to study bestsellers. He said, "I studied how the reader was manipulated by the writer. I came up with a list of techniques that I wrote down on index cards. And I used every one of them in "Coma"." He conceived the idea for "Coma", about illegally creating a supply of transplant organs, in 1975. In March 1977, that novel's paperback rights sold for $800,000. It was followed by the Egyptology thriller "Sphinx" in 1979 and another medical thriller, "Brain", in 1981. Cook then decided he preferred writing over a career in medicine.