Che Guevara pushed me over the edge. Not him personally, you understand, but rather Compañero: The Life and Death of Che Guevara, Jorge Castañeda’s biography. I read it under book club orders (and the embarrassing realisation that my knowledge of him didn’t extend much beyond: doctor, revolutionary, dead, that poster). Meticulously researched, every page was cram-packed full of detail.

In the first two paragraphs of the first chapter ‘Childhood, Youth and Asthma in Argentina’, we learn about Guevara’s birth; the size of Rosario, the city where he was born; the population of Argentina; and his (part-Irish) bloodlines on both sides for two generations. It set the tone for what was to come. Most of the pages had footnotes, creating a vast secondary text that I insisted on plodding through page by page. Perhaps the internet is rewiring my ability to read a single narrative: that twitterish, jumpy sense that one is missing something elsewhere caused me to treat the footnotes as essential hyperlinks; printed diversions to a story behind thestory.

Such a deep level of detail is at the heart of the matter. Non-fiction needs to show its workings. The skinless body is on display for all to see. It stands strong and proud, defying us to prod it, to untangle its sinew and muscles, to try and push it over. (And believe me, there’s no pushing over Compañero.)

By the time book club came around I was convinced that reading too much fiction had made me unable to understand how to read non-fiction. I struggled to follow the intricate level of detail because I was constantly chasing a narrative, and every page became a series of decisions about what I needed to remember and what really didn’t matter to my understanding.

I wasn’t so much reading as filling a trolley full of facts on which I would examine myself at the end of the book. There were over a dozen facts in the first two paragraphs of Compañero, yet a few pages later I had retained only those which I thought I’d need for the narrative (well, those and the he-was-part-Irish bit). Yet Jorge Castaneda was writing biography, not historical fiction, so of course such detailed research was the making of the book.

Often the highest accolades given to a new biography are those for detail. The PR machines crank up when a trove of previously unknown letters is unearthed; when old friends finally agree to spill their bitter beans; when the famously happy marriage is discovered to have had no more load-bearing strength than wallpaper. And that’s as it should be – the gods of biography are in the details.

In historical fiction, research becomes a foundation that must obliquely suggest a time and place and setting that just ‘is’. The set-up has to be seamless. It must be transparent while being, paradoxically, solid. It is the skeleton hidden beneath the skin. When I began to research and write What Becomes Of Us, which is set in Dublin in 1965-66 with jumps back to the world of the women volunteers of the 1916 Rising and also to working-class suffragettes in London in the early 1900s, I realised that most of what I already knew wasn’t gleaned from history books but from novels, which I had internalised as ‘information’. I couldn’t trust a lot of what I already believed because I wasn’t sure if it had originated with a historical timeline or another writer’s fictionalised version of it. The manner in which history becomes a formal thing, a structured, agreed-upon narrative presented almost in parallel to the humdrums of daily life, was to weave its way into the book as I wrote it.

In an article in the Independent a few years ago, the bestselling historian Simon Sebag-Montefiore said that he found writing his 2008 debut novel Sashenka, set in St Petersburg in 1916, “a joyous experience, no footnotes, and the freedom of emotions and imagination”. What helped him, he said, was the realisation that “historical fiction is simply fiction set in the past, and should be judged as such”.

But if we can’t foreground lots of detail, how are we to communicate what a character’s world felt like, smelt like, looked like on any given day in the past? How do we decide what contemporary note sets the tone perfectly without drawing attention to itself, and what is the writing equivalent of a cat dragging small mutilated birds through the hall, desperate for its owner to smile and pour a saucer of cream?

For starters, one can put a big, fat place-and-date on the top of the page to tell us where and when we have shimmied back in time to, but that goes no way towards meeting the needs of readers who want to know the feel of the fabric in the clothes the characters wear on their backs. Readers are quick to notice when something doesn’t feel right, and it doesn’t have to be the written equivalent of the plastic water bottle on the mantelpiece in 1924’s Downton Abbey set either.

I realised that reading history books and contemporary accounts of the times was only part of the way to research What Becomes Of Us. And so I went to newspaper archives, those yellowed (okay, microfiched) pages in which the world lives and breathes at its own – its true – pace: day-by-day. In old newspapers the stories of the world and the country play out with all their contradictions, their understandings and misunderstandings. Progress is tracked through the display of consumer goods and every small ad has a human-sized story to tell. Fiction hides its sources, non-fiction celebrates them. Yet both of us dig and explore, getting equally dirty in old soil.

The difference is that one of us washes our hands before dinner.

Following an MFA from UCD, Henrietta McKervey won the 2015 Hennessy New Writing First Fiction Award and the Maeve Binchyt Travel Award. Her debut novel What Becomes of Us is published by Hachette Ireland on April 2nd.

henriettamckervey.com