Erin Morgenstern's The Night Circus tells the story of two competing magicians trying to outdo each other in the creation of an enchanted circus. Whether you've read it and want more of the gothic atmosphere, period charm, and dazzling detail, are on the holds list for it, or just enjoy a bit of whimsy and dark Victorianism, these books should be of interest.
Jonathan Strange and Mr. Norrell , a tale of the resurgence of English magic in the early 19th century, is just as dense and immersive as the equally thick Night Circus, and like that novel features a period writing style and a fully realized magical world-within-a-world.
Her Fearful Symmetry  shares the formal, slightly sinister tone and otherworldly atmosphere of The Night Circus. Twin sisters inherit a house abutting London's Highgate cemetery, and the mysterious aunt who left it to them continues to wield an influence from beyond the grave.
Mechanique  takes place in a futuristic/steampunk postapocalypse, where a circus made up of mechanical people travels the harsh landscape. Its author's care for detailed and striking visual description and the overall gothic atmosphere are very akin to The Night Circus, and despite the time period there is an old-fashioned flavor to it.
The dueling magicians in Robert Priest's The Prestige  become not lovers (as in The Night Circus) but ever fiercer competitors, and their unbelievable secrets and magical/scientific tricks ratchet up the stakes in this elegant, tense novel. The Victorian writing style is taken even further here, and the gothic atmosphere and magic-related drama are very reminiscent of The Night Circus.
The dramatic black and white world of the lushly illustrated The Invention of Hugo Cabret  could easily stand side by side with Morgenstern's circus. At the turn of the century Hugo is living in a Paris train station and is obsessed with mechanics and automata--one of which might carry a secret message. The dark whimsicality and period charm are similar to The Night Circus.
Likewise, Amphigorey , a collection of odd, gothic works by Edward Gorey, offers a more overt visual component. Gorey's careful, old-fashioned, twisted style could have perfectly captured Morgenstern's circus world, and the overall dark, Victorian cast of the stories is parallel (if a bit more humorously done).