Fantasy about Magicians and Magic Schools...
The Night Circus
For a poignant story about competing magicians with a similar feel to it in tone and writing, read The Night Circus by Erin Morgenstern. Fantastic book and perhaps the CLOSEST similar read to Susanna Clarke's work that I've found. Definitely literary in tone and style.
A remarkable trilogy by Lev Grossman that subverts many of the fantasy tropes. It also features a precise and detailed breakdown of a magic system that's internally consistent. If you like the emphasis on learning magic following consistent rules, with a captivating story, awesome prose, and many deep themes explored, then The Magician is the best you are going to find. Arguably labeled as literary fantasy, though not so high brow that you can't enjoy it if you like more low-brow style fantasy (i.e. Sanderson books).
Moontide Magic Rise
Want more good books about 'magicians'? You may also find that you like Sean Russell's Moontide Magic Rise duology. It's kind of the same premise: magic has vanished from the world, a couple of people are trying to bring magic back to the world, etc. In my opinion, this is the closest book/series that you'll find to Susanna Clarke's work.
Magician by Raymond E. Feist. If you want to forego all the literary aspects of fantasy and just opt to a straightforward classic style fantasy about a coming of age with a young boy becoming a powerful magician, then you could also read the standard epic village boy to might magician in Feist's Magician.
Literary Fantasy (fantasy with deep themes and beautiful writing):
The Golem and the Jinni
The Golem and the Jinni. Another book you may just enjoy if you like fantastical tales that are touching and incredibly well written. Definitely considered literary fantasy.
Tooth & Claw
TOOTH & CLAW by Joe Walton. Dragons living in a Victorian Society? I dare you to try it! Read if you like the rich Victorian fantasy setting present int Jonathan Strange and Mr. Norrell.
For an epic fantasy series about fairies, you could read Shadowmarch by Tad Williams. There's lots of little folklore tales about fairies and elder creatures scattered throughout the story -- something that Jonathan Strange & Mr. Norrell has in abundance.
Good Omens by Neil Gaiman and Terry Pratchet. There's a lot of Brtitishness to this novel that you might just like if you liked Clarke's work.
If you like the slow pedantic pace of Clarke's work, the intense focus on characters and descriptions which almost seem to the point of excess but (finally) a fully realized magical world and with a gripping plot by the end of it, look no further than the majestic Gormenghast books.
For the rich use of the English language, read Lord Dunsany's magnificent The King of Elfland's Daughter. This is one of those proto-fanasy classics in the genre that few have read.
Jack Vance Dying Earth series. Science Fantasy, but oh god the use of the English language.
The Stolen Child
Are you a fan of fairies in a fantasy tale? Another book that deals with old fairy folk tales is Keith Donohue's The Stolen Child. A novel about the search for identity, The Stolen Child makes for a compelling read. The Stolen Child, like Susanna Clarke's work, is very well written. These books are sort of your "out of the box" fantasy. It's quite refreshing to see the fantasy genre has more to it than epic fantasy.