I think it would absolutely help to learn a bit about Camus' philosophy first. To me, reading it through this lens, the stranger is an exercise in absurdism. And without this absurdist background, this would just be a book about a sociopath. But it's not.

Mersault is simply fully aware of the meaninglessness of life and the complete and utter indifference of the universe towards him. So he lives indifferent to it. He's not excited about a job in Paris, because that doesn't matter to him. This is also why he isn't sad about his mother's death. He seems to be perpetually living in the now, focusing on the tangible world around him rather than emotions. At least, that's what I get from it.