I think the Christian existentialist-personalist thinkers have more insight than Sartre and Camus. The French existentialists are still worth reading, though. Kierkegaard is insightful, but difficult and one has to work through what he is doing with assumed characters as authors, indirect communication, etc. I recommend the following:
Nicholai Berdyaev, The Meaning of the Creative Act, The Destiny of Man
Gabriel Marcel, Being and Having, Man Against Mass Society
Christos Yannaras, Post-Modern Metaphysics, Relational Ontology
The Greek fellow at the end is more a fellow traveler than a straight existentialist, but he's interesting and is working through a similar metaphysical stance.