Don't remember much of the book, but "Hell is other people" or something similar is a famous quotation of his. Might hold some pieces of the puzzle for you (if there is any to solve).
"The stranger" is a favourite. Guilty as charged. Hopefully it will pass.
Yeah hell is other people (l'enfer c'est les autres). Fits me too. But this quote is from Jean-Paul Sartre, not Albert Camus. Both were existentialist writers though.