The year in which the novel is set is not explicit but cannot be later than 1951. Jim Dixon is a medieval history lecturer at a redbrick university in the English Midlands. The comedy of the novel is Dixon's rebellion against the cant and pretension he meets in academic life and the uncontrolled escalation of this from private fantasy to public display. It seems a disastrous trajectory but Jim is 'lucky' and the novel ends with him in possession of a measure of affluence, the London life he craves and the girl. Dixon is a northern, grammar school-educated, lower middle class young man and uneasy with the pseudo-intellectual values he meets in academic society. The action takes place towards the end of the academic year. Because Dixon made an unsure start in the department, he is concerned about losing his position at the end of his probationary first year. In his attempt to be awarded tenure, he tries to maintain a good relationship with his head of department, Professor Welch who is an absent-minded and gauche pedant. He must also, to establish his credentials, ensure the publication of his first scholarly article, despite having little time remaining.
Dixon struggles with an on-again off-again "girlfriend" Margaret Peel (a fellow lecturer and possibly based on Monica Jones, the sometime muse and companion of Amis' friend Philip Larkin). Margaret is recovering from a failed suicide attempt, in the wake of an unsuccessful relationship with a boyfriend. Margaret employs emotional blackmail to appeal to Dixon's sense of duty and pity to keep him in an ambiguous and sexless relationship. Professor Welch holds a musical weekend that seems to be an opportunity for Dixon to advance his standing amongst his colleagues but this goes dreadfully wrong when Dixon gets drunk and burns his host's bedclothes. At the weekend, Dixon meets Christine Callaghan, a young Londoner and the latest girlfriend of Professor Welch's son, Bertrand, an amateur painter whose affectedness particularly infuriates Dixon. After a bad start, Dixon realises he is attracted to Christine, who is far less pretentious than she initially appears. Dixon's obvious attempts to court Christine upset Bertrand, who is using his relationship with her, to reach her well-connected Scottish uncle, who is seeking an assistant in London. Dixon rescues Christine from the university's annual dance when Bertrand treats her badly. The pair kiss and make a tea date but during the date, Christine admits she feels guilty about seeing Dixon behind Bertrand's back and because Dixon is supposed to be seeing Margaret. The two decide not to see each other and Margaret's ex-boyfriend telephones Dixon and asks to see him to discuss Margaret.
The novel reaches its climax during Dixon's public lecture on "Merrie England," which backfires as Dixon, having attempted to calm his nerves with an excess of alcohol, uncontrollably begins to mock Welch and everything else that he hates; he finally passes out. Welch, not unsympathetically, informs Dixon his employment will not be extended. Christine's uncle, who reveals a tacit respect for Dixon's individuality and attitude towards pretension, offers Dixon the coveted assistant job in London, that pays much better than his lecturing position. Dixon then meets Margaret's ex-boyfriend, who reveals that he was not exactly Margaret's boyfriend at all and the two realise that the suicide attempt was faked to emotionally blackmail both men. Dixon feels he is free of Margaret and has the last laugh, when Christine decides to pursue her relationship with Dixon, because she discovered that Bertrand was also pursuing an affair, with the wife of one of Dixon's former colleagues. The two decide to leave the town in favour of London. On their way to the train station, Dixon and Christine see the Welches on the street; Dixon cannot help walking past them, with Christine on his arm and collapsing in laughter at how ridiculous they truly are.