A pretty reliable guide to how much a non-fiction book impresses me is how long it takes me to read it. With Michelle Obama’s Becoming, for example, I read it in about three days. It’s taken me as many weeks to finish reading Unspeakable …

For me, the book has two big problems. First, it doesn’t really know what it’s trying to be. It’s labelled an autobiography, and yet it’s really a rather random mix of biography, essays on parliament and – inevitably – the story of Brexit.

Of course, you can argue that Bercow’s life, parliament and Brexit are all inextricably entwined, but for me a biography is all about the lived experience of those things. Unspeakable is a little about that, but it’s much more about Bercow’s opinions about parliamentary procedure, and Bercow’s take on the Brexit debacle.

Any one of those three things could be interesting. I’d happily read an entire book by Bercow on parliament. I’d probably read a book on the untold story of Brexit. But the mix often feels frustrating.

On Brexit, the book substantially misreads its audience. We don’t need to be reminded about the various events along the way. Anyone who is going to read this book will have closely followed the whole sorry saga. What I wanted there was the behind-the-scenes stuff we didn’t see, and there is almost none of that.

On parliamentary procedure, there is not enough detail about how and why it works, and non-Brexit examples of its interesting oddities.

And on Bercow, we learn remarkably little about the man we wouldn’t have known from reading his Wikipedia entry.

You of course have to expect an autobiography to be rather one-sided. We each live inside our own narrative about our own life. But I do expect self-awareness and acknowledgement of weaknesses as well as strengths; tales of times he was wrong as well as those he was right. There are a few such examples, but really very few. I do, on balance, believe his version of the bullying allegations – it certainly has the ring of truth – but at the same time he does gloss over the fact that he has often been very rude to his parliamentary colleagues, and is undoubtedly prone to being short-tempered. I would have expected him to acknowledge that those traits are what lent credibility to the claims.

The fact that he acknowledges so few of his own failings is particularly notable when he spares nothing when it comes to describing the failings of others, Cameron and May in particular.

There are some delicious examples of his humour (‘I found I had a relationship with my whips characterised by trust and understanding; I didn’t trust them and they didn’t understand me’), but it’s not enough to compensate for the failings of the book. I’d hoped for a must-read, inside story; I was disappointed.