I have added Jack Higgins' Solo to my influences bookshelf. It is not my normal sort of book, as I am not into action, but I had bought this as a birthday present for my father. I started reading the early chapters and could not stop reading it, and unfortunately by the time my father's birthday came around the book looked very second hand,
What captivated me was the psychological introspection of the assassin, which inspired a new direction for a science fiction novel about an assassin that I had been planning since the age of 10 ( I was then about 15). My efforts to write the novel foundered on my limited motivation for writing action, and my weakness at writing believable action dialogue. I might return to the project some day, but if I do it will probably have to have all of the action removed.
You can read more about my influences on my Pinterest board.