A Kiss before Dying by Ira Levin

This is a completely brilliant thriller. It is about a psychopath of course - but the brilliant writing has the effect of cheering one up. It was written in the 1950s, which means all the medical forensics we are used to reading about now were not available, and the social mores in the story are also outdated. The pace is fast, but even so, I skipped bits because I couldn't bear the suspense. I thoroughly recommend it!