The film "Memento" deals with the disturbing issue of a man, Leonard Shelby, who is in search of his wife's rapist/murderer. .
He no longer has the ability to create short term memories since the incident of the murder occurred and in showing us, the audience, Christopher Nolan (writer/director) twists the presentation of the film by reversing the scenes. In my opinion this is to create a connection between the main character and the viewer, as neither knows what to expect next. .
Thriller is a term used for many films and is regarded as having a plot based around such things as a hero, justice or a race against time to prevent an event occurring. So it is quite vague as what the definition of a thriller is.
A Psychological Thriller is a term which best suits the nature of "Memento". It scares the audience not with blood and gore as some thrillers do, but by scaring the viewer into thinking. The unpredictability of the film gives the sense of unease which in again sets us the viewers into Leonard's position.
"Vertigo", directed by Alfred Hitchcock is a thriller which seems to have similar patterns emerging as "Memento" does. .
Both concentrate on one mans search for the answer, each causing complications along the way.
Leonard searches for his wife's killer and a cure to his amnesia, unknown that he has in fact already tracked down and murdered him. As does Detective John 'Scottie' Ferguson ("Vertigo) follow a similar path. Except that John is in search of a cure to his vertigo and the answer to the bizarre goings on of his lover. They both are in search of a cure, the only difference being that towards the end of "Vertigo", John conquers his fear, unlike Leonard who remains oblivious to the truth that surrounds him. .
Both films use another similar device which is the pattern of the story. For example, in "Memento" the story works it's way backwards so that at the end of the film we are actually back at the beginning.