In choosing a significant moment in Henry James’s life, Lodge fixed on the humiliating episode of the opening night of Guy Domville. On stage to take a curtain call, and expecting applause, James faced derision. The failure of the play was the more painful when seen in the context of the popular success of his friend George du Maurier’s Trilby. When Lodge’s book was upstaged by Tóibín’s, it was a replay, with differences, of the theme of authors’ rivalries.

Lodge’s disappointment with Author, Author carried over into The Year of Henry James (2008), in which he told the story of his defeat and Tóibín’s triumph. His latest work, A Man of Parts, seems also to have been written in the shadow of that painful episode. As in Author, Author, Lodge takes what he calls ‘a novel-shaped story’ out of the amply documented life of James’s contemporary H.G. Wells (1866–1946). The form is much like that of Author, Author, as is the focus on the author at a low point in his life. James is a minor character in this story, envied by Wells for his high literary reputation and in turn envying Wells his vast readership. Late in life, the two novelists drop all pretence of mutual respect and ridicule one another’s work.

When a novelist as accomplished and celebrated as David Lodge decides for the second time to switch genres, there must be strong reasons. Is it a case of ‘do it again and do it differently’? As with James, Lodge has done a vast amount of research. It is not new territory. Wells the political and social thinker, active in the Fabian Society, has had plenty of attention, as has Wells the man of letters. His private life, too, has been explored. His stormy relationship with Rebecca West, with whom, in middle age, he had a son, is well known. A.S. Byatt’s novel The Children’s Book (2010) includes a version of the marriage of novelist E. Nesbit and the philandering Fabian Hubert Bland, with whose daughter, Rosamund, Wells had a brief affair.

The biographical subjects could hardly be more different from one another. In choosing Wells, whose mother worked as a servant in a ‘big house’ and who made a great leap to fame and riches, Lodge takes a wider social context than in Author, Author. Instead of the austere New England bachelor, whom Lodge believes to have repressed his homosexuality to lead a celibate life, he chooses a twice-married serial seducer of young women. As the somewhat coy title suggests, the central interest is in the sexual exploits of H.G. Wells.

The story opens in London in 1944. All passion spent, Wells is facing death and pondering his past. It is here that Lodge most obviously exercises the novelist’s freedom to invent. Entering his subject’s inner consciousness, an invisible interlocutor sets up a dialogue. This strategy allows Lodge to question, explain, and judge without the overt intrusion of an authorial presence. It varies in tone from cosy, indulgent chat to increasingly sharp, courtroom-style cross-examination. Shifty, evasive, egotistical Wells loses the reader’s sympathy in the later sessions.

The story moves briskly from Wells’s first marriage to his numerous affairs. Some were what he called ‘passades’; others involved stronger feelings, especially on the part of the women. It seems doubtful if Wells ever loved any of the many women in his life. Two of them attempted suicide because of his rejection, but Wells never seemed seriously upset. Twice, when faced with an unwanted paternity, he considered somehow persuading his enigmatically patient wife Jane to divorce him, but he was relieved when other arrangements could be made.

His novels and public statements reinforced the Free Love movement, but his own ideal state was to have Jane look after his material comfort while Rebecca (and others before and after her) gave intellectual stimulus and sexual satisfaction. Writers Dorothy Richardson and Elizabeth von Arnim were mature women, but it is impossible to defend his exploitation of the naïve nineteen-year-old Rosamund Bland or the impressionable Cambridge student Amber Reeves, for whom, when she became pregnant, he arranged a loveless marriage. This, from the prophet of Free Love, looks distinctly shifty.

Lodge does not attempt to solve the mystery of Jane Wells’s forbearance. ‘What will Jane say?’ Rebecca West asks when she reveals her pregnancy. Wells expects Jane to ‘take it in her stride’. In fact, Jane came ‘very near to losing her temper’ on this occasion. ‘For God’s sake, H.G.,’ she exclaimed when he broke the news. ‘Not again!’

Too many episodes of this kind may make the reader tire of Wells’s story, echoing Jane’s ‘Not again!’. Lodge steers a risky course, close to farce at times, yet taking Wells seriously as an original thinker and a gifted novelist. From his working-class origins and sketchy education, he moved into powerful circles: he knew Asquith, Lloyd George, and Churchill, as well as many of the most celebrated writers of his time. His science fiction and other speculative writings – wild fantasies at the time – predicted aerial warfare, tanks, and the atom bomb. Something like the Internet appeared in his 1930s idea of a ‘World Brain’.

Unlike Hilary Mantel’s Wolf Hall,which leaves the reader wondering where invention starts and stops, Lodge’s novel is prefaced by a welcome declaration of his use of documentary sources:

Nearly everything that happens in this narrative is based on factual sources – ‘based on’ in the elastic sense that includes ‘inferable from’ and ‘consistent with’. All the characters are portrayals of real people, and the relations between them were as described in these pages … But I have used a novelist’s licence in representing what they thought, felt and said to each other, and I have imagined many circumstantial details which history omitted to record.

Although Lodge’s endlessly energetic, totally self-absorbed H.G. Wells is hard to like, he is never boring – as I suspect that, in a conventional biography, he might have been. Henry James would have called this book ‘a loose and baggy monster’, and so it is. But for the monstrous Wells, a shapely narrative would scarcely have been possible.

The idea of a biographical novel or ‘biofic’ is often debated. There could be few better examples of this hybrid genre than Lodge’s Wells. With cards on the table, sources announced, and imaginative interventions declared, the reader can’t complain of trickery. A near-impossible character is rendered believable, and a good deal of social, political, and literary history in early twentieth-century England comes to life in his story.