Consider, if you will, a Victorian drama in two acts.

In the first act Isabella Robinson, the unhappy wife of an uncaring husband, began to keep a diary. She wrote of her friendship with the Lane and Drysdale families, who clearly understood her situation and offered her friendship and support. Doctor Edward Lane, the husband of her friend Mary, was everything that her own husband was not. Isabella was drawn to him, attracted to him, and she was prepared to act. He, diplomatically, keeps her at arm’s length.

Isabella considered other possibilities, other men, who might fill the gap in her life. Eventually it was Edward who succumbed to her. Just for a few, short weeks. He realised that the risk to his reputation, his family, his career was too great.

And that might have been and end to it. But Isabella fell ill, and her husband went to her desk and broke the lock, looking for money. He found the diary, he read his wife’s words, and he was appalled.

And so the curtain fell on the first act.

It could have been fiction, in many places it read like fiction. But it was truth. Or at least one woman’s interpretation of the truth.

The second act was very different.

Henry Robinson was determined to cast off his wife, and to have revenge at any price. he takes the diary and offers it, first to an ecclesiastical court and then to a law court, as evidence of his wife’s adultery and degeneracy.

Kate Summerscale follows the details of both cases, and steps outside the story too. To highlight the horrible inequalities of men and women under the law. To consider the question of whether a diary can prove, should be used to prove, anything. To tell the stories of other, contemporary divorce cases. And to offer up examples of the many fictional diaries of the period.

It was all fascinating, it was all set out without a hint of prejudice, but the second act couldn’t quite hold me the way the first act had.

That might have been because I knew the period and the law too well. It might have been because I realised from the start that whoever won the case the lady’s reputation would be ruined while the men would be free to move on.

But I think that it was because I missed Isabella’s voice.

It would be easy to say that she was foolish, and maybe she was. But she was also a bright, creative woman, who had no freedom, no legal standing, and no outlet except that diary. She wrote that she wanted to leave her husband, but that she couldn’t because then her sons would be lost to her. Her words might have been honest reportage, or they may have been lurid imaginings, but she kept them to herself.

How could you not feel for her?

I just wish her story had been structured a little differently, to avoid the contrast between the two acts that jarred a little.

And I wish the subtitle ‘The Private Diary of a Victorian Lady’ had been dispensed with. It gives a rather misleading impression, particularly since the diary itself has not survived and a much bigger story is being told here.

This is a very good book, a very well researched book, a very readable book … but it couldn’t quite live up to its subject matter.