Okay, so this book is fairly long (my version was 782 pages, but other formats are even longer, over 1,000), and it is written in a Victorian style. If neither of these things appeal to you in the slightest, it seems to me you should not be reading this book. Many of the negative reviews seem to focus on this, which is strange, because that is what the book plainly advertises, and that is what it delivers. 
 I myself have trouble getting into most anything closely "Victorian" in style. I have tried a few, and toss them aside (without assuming after 50 pages, I can define why this book was 1-star quality LOL--they just weren't for me). Only one of my other 5-star choices has a somewhat similar style, and that is The Complete Sherlock Holmes. Even in Holmes, I sometimes had to force myself through paragraphs, knowing that it would always get to something that really engaged me. 
 That's what a lot of this book felt like, especially at first. Only not as good. I'm simply not very fond of the drawn out, meandering literary style. I much prefer contemporary works with a more natural flow of thought. But it was well done, and many of the seemingly episodic installments did eventually lead to things I enjoyed, even if I would have to force myself to them. It was always benefiting the unique world-building, or compartmentalized story-telling, while not quite seeming to reach a true overarching story. 
 Doesn't sound very compelling, right? But, like I said, I was enjoying it. It was strangely alluring, in its own way. I would be surprised to find I was already another 20 pages deep, even though it felt kind of slow. It was like going for a leisurely walk through a nice park--sometimes in mysterious foggy weather, sometimes bright and relaxing. I felt I would be giving this book around 2.5-to-3 stars for keeping me entertained, while being quaint and unique. 
 Then around page TWO HUNDRED the titular Jonathan Strange is properly introduced. This isn't too unusual, a title doesn't have to be about the main character. But it turns out he is the main character--at least more than anyone else. The book is truly complex, it is about many characters, it is about humanity itself, it is about the duality of Strange and Norrell. But if there is a main protagonist, if there is any character that gets more "screen time" than anyone else, it is Jonathan Strange. And he is not introduced until two-hundred pages deep! 
 And yes, I still give this 5-stars. I don't understand the choice to wait so long, aside from perhaps this being a popular style in older novels or something (I wouldn't know, I rarely read them). It made me laugh when I realized it was happening, but I was enjoying it, so whatever. I read on. 
 Strange is probably my favorite character anyway. He is plenty flawed, like most people and most characters, but he has a certain dignified irreverence, and a "liberal" understanding of magic that shakes things up. He has many engaging, interesting episodes in the war against Napoleon--all the while we bounce back to very important stories involving Norrell's conservative hold on English Magic, Strange's lovely wife, Faeiries, and many more characters who are so memorable and enjoyable but I won't bother listing. 
 While all this is going on--and while I am trying to guess at where this is all going (and being very wrong)--I am thinking, "This is turning it out rather good!" It was not an addictive page-turner, but it nevertheless enchanted me further, and reading it was far from a chore. "3.5-to-4 stars!" I thought confidently. 
 Then comes about page SIX-HUNDRED. This is where it DOES become an addictive page-turner. I stayed up late on two separate nights finishing off the final nearly 200 pages. It was suspenseful, engaging, and STILL consistently surprised me. 
 This book is NOT the typical fantasy indulgence (of which I am a huge fan). It subverts all the tropes, without being tongue-in-cheek about it in the slightest. And I'm not against the tropes--they're common for a reason, they are brilliant and they work. But this manages without them. Okay, not ALL of them. But most of them. There are few typical, predictable, archetypical characters filling their roles here. 
 And by the end of it all, a fairly unlikely but believable and very sweet love story is had (as well a NUMBER of stories of truly genuine friendship). The whole book is a story about friendship, about love, about magic, about humanity, about enmity, about forgiveness, about duality, about freedom, about redemption, about forgiveness, about life. It all comes together beautifully. 
 Even before I closed the final page, and especially after, I knew I would have to up this rating to a full and well-deserved 5-stars! A really wonderful experience! BUT, only for people that either enjoy the drawn out Victorian style, or at least can tolerate it for a grand payoff.