The Comfort of Strangers by Ian McEwan (Anchor, $15). Always a master of psychological ambiguities in relationships — and a perennial favorite of mine — McEwan here depicts a friendship gone horribly wrong. When we meet vacationing lovers Colin and Mary, their relationship has turned stagnant. The heat and passion return when they meet another couple — until their new friends take them to a chilling and violent place.

The Great Gatsby by F. Scott Fitzgerald (Scribner, $16). We're more accustomed to romantic seduction, but Gatsby is all about the seductiveness that can exist in a friendship — a theme that also inspired my most recent work. I kept this novel on my desk while I was writing Under the Influence. To keep the bar high.

Brideshead Revisited by Evelyn Waugh (Back Bay, $16). Like Gatsby, this novel explores imbalance of class in a friendship. What starts out as an innocent youthful alliance — between a son of the middle class and a charmed but melancholy aristocratic Oxford classmate — turns into the stuff of tragedy.

Notes on a Scandal by Zoë Heller (Picador, $16). This one centers on a friendship that arises between two teachers — aging, lonely Barbara and beautiful, charismatic Sheba. When Barbara learns of Sheba's relationship with a 15-year-old male student, she is caught up in a marvelously complex tangle of deception and jealousy.

A Separate Peace by John Knowles (Scribner, $14). Published in 1959 — a time when homosexuality frequently masqueraded as friendship — Knowles' classic coming-of-age novel explores the affectionate rivalry between two prep school boys of vastly different backgrounds. Their trajectories are forever altered by an accident that one boy brings on the other.

The Woman Upstairs by Claire Messud (Vintage, $15). I confess I felt a certain shock when I read this novel shortly after completing Under the Influence, because the theme — the breakdown of an unequal, unhealthy friendship — so closely matches mine. But the painful dissolution of a friendship is a universal theme. In my life, the ends of certain friendships have hurt as much as the end of any love affair.

Joyce Maynard, a noted essayist since she was a student at Yale, is also the author of the novels To Die For and Labor Day. Her new novel, Under the Influence, chronicles a troubled woman's ambiguous friendship with a wealthy couple.