Jonathan Strange and Mr Norrell has reached its conclusion, with Eddie Marsan and Bertie Carvel’s rival magicians finally coming to the end of their journey in a smorgasbord of fairy legend, period detail and peerless character acting.

The series has proven a hit with many (as its source novel did before it). But over the weeks its ratings have dropped, falling from the first episode’s 4.5 million viewers to around 1.6 million for last week’s penultimate episode. For comparison, that’s about 1 million less than talky period drama Wolf Hall managed at around the same point on the lower-profile BBC2. So what went wrong for Strange and Norrell?

Of course, high fantasy is always tricky to transfer to screen – special effects can be cheesy, and the presence of magical elements can put off some viewers. And it could be that following on from fellow period drama (and ratings hit) Poldark led Strange and Norrell to suffer from comparison to that very different series. No offence to the actors, but no-one in Strange and Norrell has quite the same draw as Aidan Turner.

Still, in my mind the problem might actually be that Jonathan Strange was just too good an adaptation of Susanna Clarke’s original novel (perhaps unsurprisingly, as she co-wrote the series with Peter Harness) – and its complexity proved a turn-off for viewers.

Back when I watched the first episode, the story was fresh in my mind as I'd only recently read the novel – so I was overjoyed to see how much of the book’s excellent detail had made into the series. But as I went on, I became convinced that people coming fresh to the series would really struggle to follow the action as we were plunged right into the heart of Strange and Norrell’s alternate history world without any build-up.

Names of old magicians, past spells and general assumed knowledge were thrown about by characters with a sort of glee, perhaps aiming for a Wire-like immersion into their language and world but actually resulting in probably confusion for anyone who hadn’t spent days working through the footnotes of Clarke’s original novel. For some, I imagine it was just too much.

And that was just the start – as time went on the TV version of Strange and Norrell sometimes became even more complicated than the book, adding new storylines for characters like wannabe magicians Segundus and Honeyfoot (presumably to justify their continued inclusion long after their book equivalents had faded into a more supporting role), or twisting book storylines like Arabella's imprisonment and Jonathan's exile to Venice to add new details.

Sometimes, it felt like the series' main goal was to get as much of the novel on the screen as possible rather than to create something new in its own right - and without streamlining for TV, I think the high-concept drama was too much for viewers who left to find something a bit more digestible.

Personally, I loved how well the series preserved Clarke's world – but catering just to fans of the book like myself doesn’t necessarily make for the best use of the material for a TV series, and I think the falling number of viewers reflects that.

Take Game of Thrones, for example – while its changes to the source material aren’t always popular with fans, some of them have served to streamline George RR Martin’s famously unwieldy novels and create truly wonderful moments that the written medium wouldn’t be capable of. Its ratings are pretty good, so maybe Strange and Norrell could have learned something there.

In any case, it’s goodbye to Jonathan Strange and Mr Norrell now – goodbye to what is without a doubt the most faithful interpretation of a book I’ve ever seen on screen, and which I'm really glad ended up being made. It was imaginative, funny and astonishingly well put together considering its budget.

But when it comes down to it, I think it also might demonstrate why adaptations usually take a bit more liberty with the source. Sometimes, God isn't in the detail.