Wow. Even though it contains fairies and is over 800 pages long. 
 Whatever you do, fantasy fans, don't recall those large format, fancifully illustrated, mock bestiaries about fairies from the 80s (do they still exist?) and pass this by. I was impressed that Jo Walton in Among Others and Catherynne Valente in The Girl Who Circumnavigated Fairyland in a Ship of Her Own Making wrote about fairies without making me gag. Susanna Clarke joins their company. 
 Her story takes place at the beginning of the 19th century in England and is written in a slightly archaic style, aka Jane Austen's (I think), though it occasionally slips. In her alternative history, magic existed in England's past but is theoretical in her story present. It is academic and respectable. Magicians are gentleman who argue over interpretations of magic's history, but do not cast spells. Practical magic is lost. When the story opens, that is about to change. Mr. Norrell, a socially graceless curmudgeon, sets out to revive English magic. His vision of what that should look like is very specific. He is determined enough to impose his vision on others, including working hard to hoard books on magic and to force others out of the profession, even if they are only theoretical magicians. As Mr. Norrell grows in stature and power, perhaps his behavior even grows ruthless... 
 Jonathan Strange is a wealthy layabout who becomes interested in magic after Mr. Norrell's emergence. He becomes Mr. Norrell's only pupil. Their different personalities lead to different visions and perspectives about English magic, past and present, especially regarding John Uskglass, a renowned king from England's magical heyday whose magical practice and power was revolutionary. 
 The story conflict is deeper than and goes beyond the rivalry between Mr. Norrell and Jonathan Strange. The point of view rotates among numerous characters and is very engrossing, most of the time. 
 The fairies remind me of what's gone on recently with vampires. Vampires were bloodthirsty savages before becoming sexy gigolos. Fairies too were transformed from their truly terrifying origins into cutesy abominations. Susanna Clarke is part of the backlash, rehabilitating fairies to their chaotic, psychotic, horrific, honorable selves. 
 My true rating falls somewhere between four and five stars. I would denounce Tolkien rather than take a bullet to the head, but without the life or death incentive I cannot concur with the blurb on the cover: "...a masterpiece of the genre that rivals Tolkien". That may be impossible to accomplish in only 800 plus pages. My quibbles with this story, however, are minor (I grew a little tired of the relationship between Stephen the butler and the gentleman with the thistle-down hair) and/or shocking (after over 800 pages, I longed for more about some specifics, such as the relationship between Walter Pole and his wife). 
 You have not read this yet? I envy you.