Patricia Highsmith is incredible, to put it simply. No one else creates such taught and fiercely contemporary thrillers, even fifty years after their respective publications.
Her prose is electrifying and her cast of characters made up of sociopaths, seductresses and fanatics are all utterly compelling. Highsmith sums her oeuvre up most eloquently in her diaries (age 21!)
“obsessions are the only things that matter. Perversion interests me most and is my guiding darkness”
You can't go wrong with her, but some of my favorites include
This Sweet Sickness (1960)
Deep Water (1957)