One of the most common pieces of advice I was given when In The Blink of an Eye debuted in 2023 was "don’t read the reviews".  That always struck me as kind but strange advice, as most other industries pay small fortunes to find out what their customers think about their products or services. Yet in the world of books, we are lucky enough to have an army of passionate and committed readers, who voluntarily give up their time to tell their fellow readers exactly what they think. Two decades ago, this practice was restricted to "word of mouth", but now we can read those words on Amazon, Goodreads, NetGalley, Instagram, X and Facebook for free.

So, despite the warnings, when my first book was published, I did read my reviews – every single one. I’d be lying if I said that I was never hurt, upset or bemused by a review – but I was keen to know what readers most liked about In the Blink of an Eye, and what I could do to improve. As it’s a crime series, I wondered if it was pacy enough, and should I be focusing more on twists? Once I had 100 written reviews on Amazon, I copied and pasted them all into a document and used it to generate a word cloud – an image of the most frequently used words, with the largest being the most common.

The message from this image was loud and clear: the two biggest words were KAT and LOCK. I had been worrying about plot and pace, so it was a lovely surprise to discover that it was the characters that readers most cared about. They loved the relationship between DCS Kat Frank, who makes decisions using her gut instinct, and AIDE Lock, an AI detective who uses algorithms and logic, and they absolutely wanted more. Their relationship was always meant to be the backbone of the series, but I’d assumed this was my own peculiar interest that I would need to reign in. The feedback from readers gave me the confidence to really lean into Kat and Lock’s relationship and develop further in books two and three.

I’d always planned for this to be a time limited series of just four books, as I didn’t want the whole instinct vs logic theme to become just a trope. There is a genuine question at the heart of this series that I felt I needed to answer: just how much can AI learn, and what happens when it does? But as the time to write book four approached, so many people were saying they didn’t want the series to end, and I became increasingly apprehensive. Had I prematurely boxed myself in, and would my readers be disappointed?

Once I had 100 written reviews on Amazon, I copied and pasted them all into a document and used it to generate a word cloud – an image of the most frequently used words, with the largest being the most common

I discussed it with my editor Katherine Armstrong and ace marketeer Richard Vlietstra at Simon & Schuster UK, who kindly agreed to carry out a readers’ survey. As well as finding out a bit more about my readers (75% women, mostly aged 35-54 and educated professionals who are big Lisa Jewell fans, since you ask), I also discovered what they most wanted from book four, Body of Lies. In the free text responses, there was an overwhelming consensus: my readers wanted a final answer to the question of whether Lock is essentially good or dangerous.

Interestingly, when we asked them what ending they wanted, the responses were almost equally split between those who wanted Lock to turn out to be good, and those who wanted him to go rogue, but one thing was clear, readers wanted closure on the story arc – they needed an answer to this fundamental question and they wanted a thrilling, shocking and character-driven finale to the series.

The feedback from the survey – which was echoed in a special Zoom discussion with hardcore fans shortly after the publication of Human Remains (book three) – gave me the courage and the ambition to be bold: the high expectations of my readers meant I had to raise the game on the ending I had already planned.

Whether or not I achieved this is for the readers to decide, as Body of Lies publishes this week. But I cannot thank them enough for the feedback they have gifted me with throughout this series. In 1970, social policy guru Richard Titmuss wrote a seminal book about the voluntary system of blood donation in the UK, describing this altruistic act as "the gift relationship". It strikes me that this is an apt description of the thousands of readers, reviewers, bloggers and booksellers who take the time to not only read the art we create, but share what they think, and most of all, what it made them feel. It is a gift: and one which I am extremely grateful for.

Body of Lies by Jo Callaghan (Simon & Schuster UK) publishes in hardback, e-book and audio on 21 May 2026.