Rome recast for today as Eagle of the Ninth is adapted for big screen

Finally, 57 years after it was first published, and nearly 40 since I first sat riveted by my new find in the village library (remember them?), Rosemary Sutcliff's seminal novel of Roman Britain, The Eagle of the Ninth, has made it into onto the big screen as a Kevin Macdonald movie, The Eagle. I haven't seen it yet. I will, of course, but with trepidation, not only because the online reviews are less than favourable, but because – let's face it – the worst books generally make the best films and this was an exceptionally good book by anyone's standards.

Sutcliff herself said that her books were designed to be read by "children of all ages from eight to 88", but she didn't, I think, fully understand the impact of what she had written. Log on to any historical website, talk to any group of amateur or professional archaeologists or historians, and say the magic words, The Eagle of the Ninth. You will find that a good percentage of those present will agree that their entire life's path has been moulded on a single reading at a formative age.

There are academics whose career began because Sutcliff – and this novel in particular – sparked an interest that has never waned. There are others for whom she was the greatest and the best, and they are still trying to find a book to read that matches up to the childhood magic. And there are those of us who are still trying to write a book that will conjure that same childhood magic.

I was eight years old when I read it, but it opened doors that have never closed. I was captivated not so much by Marcus Aquila and his quest for the lost eagle of his father's legion, but by Esca, the captured Briton, and the barbarian tribes that lived north of Hadrian's Wall. They were wild, savage and magical; they spoke to seals, to horses, to hounds and conducted shamanic ceremonies that were closed to outsiders. I was an outsider and hated being so.

I wrote the Boudica: Dreaming series of novels as an entry back into that world; a way to experience the rites of passage that were so critical – and yet so hidden – in much of Sutcliff's world. Writing allowed me to map out a possible past on the premise that if this is who we were, then this is also who we could be. Which is always the point.

Ending the series, I thought that I'd said all I could say – that it was time to let Sutcliff go and stop trying to fill unfillable shoes. Until last summer, when I started to plan out the third book in the new Rome series, and discovered that The Eagle of the Twelfth was sitting there waiting to be written. Some days in, a writing life are hard work, but some are sheer, unadulterated magic. This was one of those.

Sutcliff based her narrative on the then-recent finding of a wingless legionary eagle beneath an altar stone and coupled it with the myth of the Ninth legion's disappearance around 117AD. Scholars now will tell you that there's no evidence the Ninth was ever lost, and reasonable evidence that it was simply recalled to Rome at a time when nobody was paying much attention; that it vanished from history rather than reality.

But the Twelfth legion definitely did lose its eagle to enemy forces at the massacre of Beth Horon and, given that it survived in later centuries, must have got it back again. From such grains, do novels grow – and they grow remarkably fast. I have waited 40 years to write this without realising I was waiting, and now that it's done, I can confirm that when an author says that a book wrote itself, they're not necessarily lying.

Before I could begin, of course, I had to re-read the book I had loved in my childhood. If this is going to be an homage to a great writer – which it is – it was important to know the rhythms of speech, the flow, the narrative drive; even to find out if it was written in first-person or third, because I never noticed that kind of thing in the headlong rush to finish the story.

For the record, it's written in first-person from a Roman viewpoint; and it's every bit as amazing as I remember: short and lyrical and beautiful and full of the small anachronisms that have only become apparent as our understanding of Roman arms and armour has grown. None of which matter in the least.

But what struck me most was the inherent misogyny and low-key racism; the base assumption that the Empire (it's a very British Empire) was the epitome of civilisation; that the Pax Romana was a Good Thing and that the natives were ignorant illiterates - noble savages with barbarian leanings – who were capable of being trained into service if you treated them kindly. The parallels between Marcus's taming of Esca, the captured warrior, and of Cub, the wolf he rescues from a hunt, are striking now in ways I never noticed as a child.

And then there's the barely-visible women: the home-makers and hearth-keepers, nurses, harridans and slightly wet young girls who stayed home nursing the wolf cub, waiting for Our Hero to make his triumphant return, come to his senses and offer marriage – which is also a Good Thing. Even the barbarian women may have been Wildly Wanton, or Wisely Knowing, but were basically two-dimensional and dull, while the men were striking and interesting and full of complex colour.

This is not a criticism of Sutcliff; she was born in 1920 and her formative years as the daughter of a naval officer undoubtedly coloured what was already going to be a colonial, anthropocentric viewpoint. She saw her fictional worlds through the prism of the world she understood. We all do that; it's what historical writing is about, and the only question is the extent to which we know we're doing it.

No; what astonishes me, what leaves me breathless, is that I didn't notice it at all as a child. I would like to think that today's child – of eight to 88 – would read with more open eyes. After which she or he might want to explore our modern writers for comparison. Fortunately, there are rather a lot of those.

They're not all women these days; in fact, very few of them are. There's Lindsey Davis, of course, but she's more Chandler than Sutcliff, with Marcus Didius Falco striding through 20 novels as a first-century gumshoe detective in sandals. Still, like Sutcliff's, her books skirt around sex and violence in ways that won't offend a pre-teen audience. More accurately, given that most pre-teens have been downloading porn on their mobile phones since they discovered the use of opposing thumbs, the books won't offend their parents - while offering private eye mysteries in a Roman setting for adult readers.

Ruth Downie's stories of a down-at-luck army doctor who endeavours to make his fortune in a remote corner of the Empire (Britain) are entertainting and engaging and have strong echoes of Sutcliff's work. The latest, Ruso and the River of Darkness, is a great read; while Stella Duffy's outstanding, Theodora - the true tale of the dancing girl who became an Empress - is well on its way to becoming a classic.

Then there are the men. In this field the fiction was once dominated by women: Mary Renault is the other pillar of everyone's library and I would still vote Dorothy Dunnett's King Hereafter as one of the great historical novels of all time. Yet the men are far more numerous now. There's a tendency to assume that it's all clashing swords and sweaty semi-consensual sex, with linear narratives, dialogue that never stretches into complicated territory such as subclauses, and cheerfully two-dimensional characterisation. But there are some real gems out there.

Among them, Paul Waters stands out as a writer of vivid, insightful novel. His characters are notable for their depth and emotional intelligence, and his prose style is glorious. His latest, The Philosopher Prince, comes close to Mary Renault in its language, depth and style. In a grittier, faster-paced vein, Ben Kane's Forgotten Legion series takes us to Parthia via the nastier sides of Rome. Kane writes with a freshness and verve that makes his novels well worth reading.

Similarly, Douglas Jackson's Roman trilogy reaches its conclusion with Hero of Rome, set in Britain at the time of the Boudican revolt. That is always an interesting period, even if you do come at it from a pro-Roman angle.

John Stack's excellent new Masters of the Sea series takes us into the Roman navy. If you find that you're at home in the maritime environment, and care to look at the disintegration of the Roman Empire through the eyes of those who followed it, treat yourself to Robert Low's Oathsworn Viking series. It is, to my mind, one of the worthiest successors to Sutcliff's mantle: raw, real and riveting. You can't get better than that.

'Rome: the Emperor's Spy' by MC Scott (Manda Scott) is published in paperback by Bantam. 'The Eagle', directed by Kevin Macdonald, goes on release on 23 March