Of John Osborne's themes in Look Back in Anger, I would single out two as having special importance.
First, the play deals with class conflict. Jimmy, though he has been to university, despises the middle-class values of his wife Alison's background. There is a self-consciousness about this, as in the works of other left-leaning writers. For example, Jimmy has much in common with several characters in George Orwell's early novels, such as Gordon in Keep the Aspidistra Flying. A young man like Jimmy has the potential to "make something of himself," to do much more than run a market stall. However, he chooses not to, because to do so is to "enslave" oneself to money, which is the typical thing middle-class people do.
Next, I would examine the theme of sexual morality and gender issues as they relate to a person's individuality. By our standards today, Osborne's attitude—or at least the attitude expressed through Jimmy's character—seems chauvinistic and primitive. Jimmy is abusive to both Alison and her friend Helena and treats both of them, to some degree at least, as objects. His behavior, however, is a corollary of his general rebelliousness and his resentment of "middle-class morality." Hence, his flouting of convention by starting an affair with Helena. The irony is that even this aspect of Jimmy's rebellion was seen by many as a progressive quality in the 1950's. His revolt is against conventional morality, but as stated, it also results in his demeaning women and being abusive to them. Jimmy also treats his friend Cliff as a kind of sidekick upon whom he takes out his frustrations. Altogether, even if we take into account Osborne's outdated approach to gender issues and somehow make allowances for it, we can see that Jimmy's behavior is chiefly one of displaced aggression. The demands of the system, of the establishment, in which a man is expected to subvert his individuality and independence, end up causing him to demean other people around him, both men and women. Did Osborne intended his "message" to be understood this way? Perhaps not, but from our present-day perspective, this is a valid interpretation: the unfairness of class differences and the demands of the economic system have caused a man such as Jimmy to victimize other people—his wife, his wife's friend, and his own friend—and Jimmy simply makes himself more miserable in the process.