L'étranger (The Stranger) is a pre-existentialist novel by Albert Camus. It is about a man named Meursault. Here's a quick and dirty analysis of themes from chapter 1.

Aujourd’hui, maman est morte. Ou peut-être hier, je ne sais pas. J’ai reçu un télégramme de l’asile: «Mère décédée. Enterrement demain. Sentiments distingués.» Cela ne veut rien dire. C’était peut-etre hier.
Meursault is practically emotionless. His reaction to his mother's death in the very first paragraph of the book is to say, "Today, Mother died. Or maybe yesterday, I don't know. I received a telegram." His lack of emotions makes his reactions to everything ridiculous.
J’ai bu. J’ai eu alors envie de fumer. Mais j’ai hésité parce que je ne savais pas si je pouvais le faire devant maman. J’ai réfléchi, cela n’avait aucune importance. J’ai offert un cigarette au concierge et nous avons fumé. ... J’ai eu un moment l’impression ridicule qu’ils étaient là pour me juger.
Meursault is very rational. He knows that he should not smoke next to his mother's corpse, but he thinks "it doesn't matter." He knows that he is going against the hidden rules of society; he understands that he is different. We can see that this affects him negatively because he feels ashamed enough to think that he is being judged. He also apologizes for himself often, like when he wants to justify his need for two days off to his boss. He says, «Ce n'est pas de ma faute,» which means, "It's not my fault." Meursault is a very honest person, a characteristic that later causes him a lot of trouble. This is shown by how he describes exactly his reasoning, and acts on his intentions, even though he's ignoring how he thinks he is supposed to act.
L’éclat du ciel était insoutenable. A un moment donné, nous sommes passés sur une partie de la route qui avait été récemment refaite. Le soleil avait fait éclater le goudron. Les pieds y enfonçaient etet laissaient ouverte sa pulpe brillante. Au-dessus de la voiture, le chapeau du cocher, en cuir bouilli, semblait avoir été pétri dans cetter boue noire. J’étais un peu perdu entre le ciel bleu et blanc et la monotonie de ces couleurs, noir gluant du goudron ouvert, noir terne des habits, noir laqué de la voiture. Tout cela, le soliel, l’odeur de cuir et de crottin de la voiture, celle du vernis et celle de l’encens, la fatigue d’une nuit d’insomnie, me troublait le regard et les idées.
Meursault is very affected by nature. This entire passage, occuring on the march to the cemetery, shows how he is unable to stand the heat from the sun, the smell of the tar on the pavement, and the monotony of the colors in his surroundings. He often defines his emotions through how his surroundings affect him. The closest he comes to happiness is in the absence of pain, from his surroundings or from the people he knows. He feels a great relief when he goes back to Algers only because he is escaping an uncomfortable situation. We see later how his urgency to escape the discomfort caused by heat and light and how he is controlled by this causes him to shoot a man he did not intend to shoot.