The origin story of Children of Earth and Sky, my current novel, begins with my Croatian editor being the first person ever to tell me about the Uskoks of Senj. He did that as we approached where their stronghold had once been on the Dalmatian coast (the Uskoks are long gone now, a small tourist town remains). I told that road trip story here and another version of the origin story here. By the time I came, many years later, to write a book taking off from that anecdote, the tale did not involve Uskoks, or the Dalmatian Coast. Nor was it formally about the aftermath of the Ottoman conquest of Constantinople, or the Holy Roman Empire, the Republics of Venice or Dubrovnik. And Senj had become Senjan.

Close, but…

I do this all the time. A modus operandi by now. Nearly our known history, but not quite. A 'spin' on the past, or a 'quarter turn to the fantastic', as one reviewer called it.

Provence becomes Arbonne in my novels; Al-Andalus, Al-Rassan; Byzantium, Sarantium; China's Tang Dynasty morphs into Kitai's Ninth…

I've written over the years about how this approach evolved, what underlies it, but just about every interviewer, for print or pixel, on stage or on air asks again, and it reminds me that just because you've said something somewhere, it doesn't mean everyone (or even most people!) will have seen it. I can feel over-identified with certain topics, and a large majority haven't a clue I've said a word about them! It is a corrective. A comment on the nature of our world.

So, on the eve of a new book's release, as that journey from Senj to Senjan leads to Children of Earth and Sky, it seems proper to address the 'why' of such a journey. Why isn't the book set in a 'real' place, in our own Europe? Why do I have Seressa instead of Venice and Batiara for Italy? Why a rebel leader named Skandir, instead of Albania's great Skanderbeg, who inspired my character?

There are a multiplicity of reasons by now. But here's a caveat: be skeptical when writers present intuitive processes as thought-out planning. This was an evolution for me, not a strategic concept. I discovered what I was doing, and why it worked for me. I didn't lay it out in advance.

It largely started at the beginning of the 1990s with A Song For Arbonne. (Tigana, the book that came before, was far more loosely tied to real places and events.) For Arbonne, I read widely in the poems and the lives (as we know them) of the troubadours, and in the history of the Albigensian Crusade and the 'Courts of Love' of medieval Provence.

I emerged with a number of thoughts, some of them about how the role and status of women in the west took a turn with the conquest of Provence, and how a great deal of political history might also have also done so. I invented troubadours inspired by a few of the real ones, and then I reversed the result of that 'crusade' down the Rhone valley. There is almost nothing of the fantastical in the book, the idea of magic is treated as a false, cynical 'tool' of organized faiths to frighten and control people. I sharpened the male-female aspect by offering a northern sun god and a goddess in the religion of the south.

And I found that I liked what all this allowed me to do. I could work with history but tighten focus on themes. I could have my characters do and think and be what I wanted them to, because they were not the real people. Readers who knew the history would see the riffing involved, those who didn't would either not miss it or – a bonus, for me – might be moved to do some non-fiction reading of their own, after. (And I always include starter bibliographies.) The historical reversal in Arbonne embodied a thought-experiment. I tried to do it lightly, to let the reader go as far as he or she wanted down that road. If they preferred to just treat the book as a tale … well, each reader makes the book they read. (That's another essay.)

With Lions of Al-Rassan, which followed, new elements came in. This time my research led me to Rodrigo Diaz (El Cid), probably the most potent figure in Spanish history, mythic or real. The intellectual battle as to which of those he really was, and to what degree, lasted well into the 20th century and was bound up in the politics of and after the Spanish Civil War. I also discovered ibn Ammar, the great courtier-poet of Al-Andalus, and I found in my research, to my great delight (it shaped a novel) that these two extraordinary men appeared to have been exiled in the same year by different kings to the same place. Not such a big city, very prominent men, they'd have to have met, I thought.

But I realized that I did not want to treat history and real lives as if my own 'have to have met' idea was a truth. I didn't want to set about giving real men invented personalities, relationships, desires and thoughts I imposed on them. And yes of course 'imposed' is a loaded word, and yes many brilliant books have been written that do exactly this.

I didn't want to do it that way, though. I saw, for myself, a different approach to the process. Perhaps (probably?) it was because I had begun as a published writer with a traditional fantasy years before, but the creative avenue I was seeing, along with the opportunities it afforded, kept suggesting this quarter-turn to me.

I made the setting for that book Al-Rassan, not the actual Al-Andalus. I had characters evoking the two lions I'd researched (and other real figures, too) but clearly not them. I invented a female physician. There were historical parallels, and I let my setting give me license to push her a little further. And – perhaps most of all for this book – I changed the three religions of our history.

I wanted to explore interactions not ideologies. To see if the hint of the fantastic allowed me to detach readers somewhat from assumptions, prejudices. If the twist of the fantastic could become a tool serving the emerging heart of the novel: the way in which holy war can destroy the space in which men and women – even powerful ones – might move, and shape their own lives and relationships.

It was with Lions that I started to clearly see – and begin to speak about – the strengths of fiction done as near-history as opposed to history. One aspect of this that resonated strongly for me was how it displayed (I dared hope) respect for the real people behind a story. I was inspired by them, not pretending to assume psychological awareness of them. With a figure like El Cid, still so powerful for a culture, it seemed proper to work this way, and it became liberating, too. Then, just as I'd reversed the Albigensian Crusade in the previous book, I telescoped the Reconquista in Lions. The tragedy of a culture's demise could play out in one or two generations in a novel, not over hundreds of years. Sharpening the focus, again. I was learning the sorts of things I could do with this approach.

I suppose I've never looked back. The Sarantine Mosaic added elements to the concept, as I began to think more formally now, and write about these issues, especially the idea of not using real people in fiction.The Mosaic pair was where I pushed the idea hardest, perhaps, that my characters and setting are modeled on our world's, but not identical. Justinian and Theodora's Constantinople, the building of Hagia Sophia, and Justinian's Italian Wars … All these were recognizable, but altered, because the books are about Sarantium, not Byzantium, and I had thoughts I wanted to develop and explore that way. About Procopius the historian, about the writers of history, chroniclers and artists, about those artists and the powerful, about Yeats, about random events that can change the world (that's a recurring motif for me).

I had come to realize that this quarter-turn gave me a remarkable degree of freedom in a book. I gained the ability to comment on, interact with, real history. It felt empowering, while retaining the core idea of preserving respect for real lives. Also, on a very basic level – but one that matters if you want to keep readers turning pages – this shift from following the events of history means that even if a reader knows the real story of what happened, he or she cannot be sure they know where the novel they are reading is going. This is, I have often said, a gift to both writer and reader.

As a result, by the time I wrote Last Light of the Sun, and then two novels inspired by Tang and Song Dynasty China, I'd had years of thinking about these issues, seeing and shaping ways in which I could add to the concepts, even comment on my earlier work. Ysabel had offered another way to comment on history, but is an exception for me, taking place in our modern world, in the south of France: a book that insisted on being written when we returned to Provence after a decade away. It had not been the project I went there to write. Sometimes that happens.

So, briefly told, these are some of the strengths I see in quarter turns. There are also downsides, or risks, to how I work, and I'd be remiss to overlook them. Readers will never learn the year of the Treaty of Utrecht in my novels. They will not assuage any desire to 'learn the real facts' about a specific period, the way they might while reading a straightforward historical fiction. Of course those 'facts' might have been altered by the author, sometimes significantly. On a mundane level, we readers like categories. Bookstores certainly do, including online ones. If my work slips back and forth between historical fiction and fantasy with themes of today … shelving gets challenging, marketing does. Even labelling does.

One agent said to me long ago, 'Write me a straight historical and watch the advance we get, how many copies we can get sold for you!'

He may have even been right. I'm not certain, but he was a commercial agent and he was referring to exactly this border-blurring aspect of how I write, this challenge to pinning the books down. In the end, I knew then (and still know) that I was a stubborn prairie boy who enjoyed what I did too much, that I saw (and still see) too many strengths emerging from this approach. And I'm reassured, over a great many years now, by so many loyal, thoughtful, 'I get it' readers around the world and in many languages.

I carried on back then. I still am. This has laid out out some of the reasons, for those coming late, or just trying to sort through for themselves why Senj becomes Senjan.

Guy Gavriel Kay is the international bestselling author of twelve previous novels and a book of poetry. He has been awarded the International Goliardos Prize for his work in literature of the fantastic and won the World Fantasy Award for Ysabel in 2008. In 2014 he was named to the Order of Canada, the country's highest civilian honor. His work has been translated into more than twenty-five languages. His latest novel, Children of Earth and Sky (New American Library; Hardcover; $27.00) is on-sale now.

For more information, please visit brightweavings.com and follow Guy Gavriel Kay on twitter @GuyGavrielKay