@GT: Whenever people talk about existentialism, I just quote the first line of Camus' novel 'The Stranger',"Mother died today. Or yesterday maybe, I don't know".  This observation of the hero, Meursault , of the novel  weaves the entire scaffolding of existentialism for me. I will put the philosophy in simplest possible words : senselessness and purposelessness of life in an absurd world. Camus'  must have had his share of mammoth  tragedies  in his life and time  to gift humanity with such a harrowing philosophy. I read 'The Stranger' right after my high school. The book would haunt me for a long time to come and had a deep imprint in my thinking mode until more practical experiences of life had better lessons/philosophy to teach me.

    So, if one is looking for an authentic work on existentialism, 'The Stranger' is a better pick than 'The Plague'. In 'The Plague', Camus transcends the chilling aloofness of existentialsm and embraces love  which makes it all the more beautiful.  I promise that would be your life-time reading . Please, go for that and share your experiences here.You might just meet the best fictional hero in ' The Plague' - Dr. Rieux. A character which you would never forget.