Thérèse Raquin is Émile Zola's most famous novel outside of the Rougon Macquart series. It was first published in 1867, four years before the first of the Rougon Macquarts - The Fortune of the Rougons, though, as with Zola's very first novel Claude's Confession (1865) one can see very clearly the themes that would dominate his later works.
In the preface to the second edition (1868) Zola wrote this rather barbed comment:
I was simple enough to suppose that this novel could do without a preface. Being accustomed to express my thoughts quite clearly and to stress even the minutest details of what I write, I hoped to be understood and judged without preliminary explanations. It seems I was mistaken.
He goes on to write a defence against the "churlish and horrified outcry", stating,
In Thérèse Raquin my aim has been to study temperaments and not characters. That is the whole point of the book. I have chosen people completely dominated by their nerves and blood, without free will, drawn into each action of their lives by the inexorable laws of their physical nature. Thérèse and Laurent are human animals, nothing more.
It's hard not to notice the parallels of this and the preface of The Fortune of the Rougons:
My aim is to explain how a family, a small group of human beings, behaves in a given society after blossoming forth and giving birth to ten or twenty individuals who, though they may seem at first glance totally dissimilar from each other, are, as analysis shows, linked together in the most profound ways. Heredity, like gravity, has its laws.
By solving the dual problem of temperament and environment, I shall attempt to discover and trace the thread that leads mathematically from one person to another.
Now I've read Thérèse Raquin a second time, having read the majority of Zola's novels (of his novels, I only have Les Mystères de Marseille, Madeleine Férat, and Les Quatre Évangiles left) this idea of Thérèse Raquin being a study of temperament is very obvious and the novel is in that sense (and most others!) classic Zola. But when I first read it in 2012 the only other Zola I'd read was Germinal (1885) and I knew nothing about Émile Zola or his aims, and I don't think they actually are that obvious. One can forgive the first audience for their disgust and well understand the French writer Louis Ulbach describing Thérèse Raquin as "putrid literature".
Whether one is aware of the aims or not, Thérèse Raquin is a shocking novel. The main character Thérèse lives with her aunt, Madame Raquin, and Madame Raquin's son Camille, a spoilt and sickly boy about the same age as Thérèse. At the age of 21 the two marry, a match set up by Madame Raquin, and they move to Paris so that Camille may pursue a career at the Orléans Railway Company. This brings to mind Zola's later novel La Bête Humaine (1890) in which the railway represented both modernity and the unnatural and dangerous. The similarities continue in Thérèse Raquin: when she and Camille's friend Laurent begin a passionate affair they decide that they will kill Camille, but after his murder (they drown him), they are driven completely mad by guilt.
In terms of plot alone, I enjoyed Thérèse Raquin. It's a dark, even Gothic novel along the lines of Edgar Allan Poe. The setting is bleak, the crime horrific, and the consequences nightmarish. It's a psychological drama, the couple are haunted by hallucinations of Camille's ghost, and they cannot live with what they've done, let alone live happily with one another. But, Thérèse Raquin is much more than that, as Zola rather caustically points out in the preface. Thérèse is of Algerian descent, a short hand of these old books to suggest a 'hot', passionate temperament (like that of, say, Othello in Shakespeare's play). Her father is a sea captain, suggesting an adventurous and energetic streak, yet this aspect of Thérèse's character, which is inherited from her mother and father, as with all the Rougons and Macquarts of Zola's later novels, is suppressed and she is left a deeply repressed character who becomes very nervous and high strung (reminding me a little of the Rougon Macquart matriarch Adélaïde Rougon). By way of contrast, her lover Laurent is self-indulgent and overtly sexual and Camille asexual (his own temperament is explained too by his over-bearing mother). These three temperaments collide, leading to tragedy, and we see in the novel not only the manifestation of these temperaments before a crisis but also after, and how both Laurent and Thérèse deal with their guilt. In a sense, they are a victim of both heredity, temperament, and circumstance, something Zola explored further in the context of the Second French Empire in the Rougon Macquart novels. Like Jacques Lantier of La Bête Humaine, they are unrefined animals, thinking selfishly and reacting to their desires with little thought of the consequences. But what separates us from animals, so they say, is guilt, which turns into paranoia (seen in their treatment of the family cat François) and hysteria. However their guilt is more primeval: their treatment of Madame Raquin, Camille's mother, following her stroke does not suggest a genuine need or attempt at redemption, it is a terror of punishment be it divine, supernatural, or judicial. The idea of free will is very much in question, not something I necessarily agree with but a popular question in the 19th Century.
I do love Thérèse Raquin, yet I can easily see why someone would hate it or not wish to read it. It is a very disturbing novel and goes beyond the Gothic novels of the time. It's very clever, but does lack subtlety, not something I particularly mind but others may.