On the back of my copy, there's a review by Gaimen which calls this the greatest English language "fantastic" novel in the last 70 years. This is perhaps strong praise but I would certainly call it one of the better contemporary reads. It is, however, aimed very much at academics;
In other reviews, the characters are called unsympathetic, which couldn't be farther from the truth from my point of view. The book opts to make the two magicians into eccentic scholars; never dry academics or wild romantics but instead a very human combination of the two. Both of them represent the kind of scholarly personalities of the time which exist to a degree even today, they may remind you vaguely of teachers or historical thinkers [the inclusion of Byron was helped show the contrast here]. Both are deeply flawed and consumed by research in their own way and their flaws aren't glorified or glossed over, giving the feel of a rounded personality.
However, this does not come out readily and the characters do not become apparent foils until later. My view was one that the book mocked a little as I constantly expected wilder magicians if only to serve as foils to the scholarly ones; the reclusive Norrell to the theoretical magicians then Strange to Norrell. These characters are
different but the deeper differences do not come out readily; this makes for more nuanced characters but a less exciting beginning.
The style itself is after Jane Austen whom I was never fond of, but the surreal premise of the book makes it read as a parody-pastiche which is pleasant for both fans and detractors. The attitudes of the time are mocked without venturing too far from character and though a couple remarks in the last volume over did it a little, I usually found myself laughing. The lemoniness of the narrator does make me feel like this piece is less timeless for it but they added to the experience for me.
The book is dense and nuanced, written as a pastiche of Jane Austin with numerous historical references about complicated and flawed characters that are ultimately just two quarreling academics in a field no one else understands. It's clear that this book isn't intended as a common audience book in the same way as Harry Potter but if this review sounds positive to you, then it is probably going to be up there with Tolkien for your favourite Fantasy reads.