At B & N Reads Somers tagged "five characters that are basically superheroes, despite appearing in books that aren’t in any way speculative fiction," including:
Marathon Man, by William GoldmanRead about another entry on the list.
Goldman’s classic 1970s thriller not only inspired one of Laurence Olivier’s most memorable film performances (the phrase “Is it safe?” is still a monumental buzzkill), it introduced the titular character, real name Tom Levy, into the cultural landscape. Through no fault of his own, Levy is caught up in a world of espionage and assassination, and makes it through only because of his superpower: superhuman endurance. He survives horrific torture and manages to triumph in the end only because he can keep going when his enemies have to slow down to catch their breath. If you’ve only seen the movie, the book is not only more tense and exciting than you might think, it’s also much less sweaty than you might expect (although still plenty sweaty).
Marathon Man is on Paul McEuen's six favorite books list and Howard Gordon's list of the five best thriller plots with terror themes.