American Werewolf has a great sense of humor to compensate the often bleak story line. The movie opens with two American students David (David Naughton) and Jack (Griffin Dunne) hiking through the English countryside and are attacked by a werewolf. Wiseguy Jack perishes, but David survives.
While recuperating in the hospital David experiences terrifying nightmares and receives visits from an "undead" Jack. Dunne often gets the best laughs and is menacing as athe ghoul. David begins a romance with a sympathetic nurse wonderfully played by Jenny Agutter who brings warmth and humanity to the picture.
American Werewolf works for me, because like The Exorcist and Rosemary's Baby, there's a strong sense of reality thanks to the on location shoot. The heightened reality increases the sense of horror and the emotional toll. The wrenching transformation sequence, which took weeks to film, stands alongside John Carpenter's The Thing for most intense use practical effects.
An American in Werewolf in London remains the best of its kind for the jarring shifts in tone from comedy, romance, and horror. Many have tried to copy it without success.
Notice how the trailer plays up the horror elements.