I hold Agatha Christie entirely responsible for how I've ended up. The Murder at the Vicarage was the only book my grandparents possessed (apart from the Bible) so it was the only port of call for me after I'd finished whatever library books I'd brought with me when I came to stay. I got hooked on the detective novel thanks to Christie but I never considered myself to have much in common with her as a writer.

It turns out we're more alike than I thought. Thanks to the revelations in John Curran's new book, Agatha Christie's Secret Notebooks: Fifty Years of Mysteries in the Making, I've discovered some quite worrying congruences.

Seventy-three of Christie's notebooks survive. They're not a collection of identical, leather-bound, hand-tooled books with Florentine endpapers and heavyweight paper. They're a miscellaneous jumble of school jotters, pocket-sized pads and shorthand notebooks. A bit like my own diverse selection, currently comprising: spiral bound, plastic covered with a snap fastener from Dynamic Earth; a small black pocket-sized pad with an elastic band to keep it closed; an A4 Pukka Pad; a leather-bound notebook bought in a tiny shop in Siena. One lives on my desk, one by my bed, one in my backpack and the other floats around, turning up where and when I least expect it.

So while academics may puzzle over the reasons why notes pertaining to a particular novel of Christie's appear in more than one notebook, I understand the phenomenon perfectly; it happens to me all the time. An idea for a plot twist or a great line of dialogue or a character's name or a telling incident comes in its own good time. When I fear losing it, I scribble it down in the nearest notebook – so one novel's notes end up in several places.

Furthermore, it can take years for an idea to ferment into a full-blown story. Some of Christie's notes for a specific book span years. I know that feeling. On occasion, it's taken me a dozen years or more from the first seed to the point where I'm ready to start writing. And as with Christie, my original idea can evolve through several possible shapes before it settles into what feels right. If we're lucky, the finished book should feel inevitable to the reader – as if no other outcome were possible. The reality is that writers try on lots of possibilities before we find the one that fits.

And then there's all the stuff that intervenes. Writers don't just write. We also have lives, with responsibilities and Stuff To Do. So Christie's notebooks are peppered with the things that intrude. A list of dahlia varieties she needs to obtain for the gardener; a reminder of kitchen equipment she needs to buy for the house in the country; phone messages she needs to return. Just like mine. The notes for my latest novel Fever of the Bone are interpolated with a list of plumbing supplies; a menu and shopping list for a weekend when we had a houseful of visitors; train times from Northumberland to Inverness.

There's one other shaming similarity between the evidence of Christie's process and my own. We both have appalling handwriting. That John Curran has been able to decipher Christie's is a monument to his dogged commitment to his task. God help anyone who ever decides to decode mine. I can't even read it myself if enough time's gone past.

Sometimes it's a complete bitch having to trawl through half a dozen chaotic notebooks to find those key elements that felt significant enough to write down. Until now, I thought I was alone in the chaos of my process. I imagined all my fellow writers with neat box files and alphabetised notes, databases maintained with military precision. But now I know there's precedent – and what a precedent. It's cheered me up more that I would have believed possible to realise that behind all that perfect plotting lies at least as much chaos as I embrace in my own writing life.

Val McDermid's latest novel, Fever of the Bone, is published by Little, Brown this week.