Readable

In the comments to "Symptomatic," Marya asks, "which of your religious novels are actually fun, quirky reads, as opposed to slogs?"

"Fun" and "quirky" aren't usually the adjectives that come to mind when my religious novels are involved, but some of the authors are perfectly readable.  A few suggestions, in alphabetical order:

• Grace Aguilar.  Not a brilliant prose stylist, but her plotting and characterization are OK, and it's interesting to see a Jewish novelist trying to grab both the Protestant and the Jewish readerships at the same time.  Michael Galchinsky's recent anthology is a useful place to start.
• Elizabeth Rundle Charles.  Specializes in fictional diaries, frequently with multiple narrators; her representations of spiritual experience are often genuinely moving, and the characters are more nuanced and three-dimensional than the usual.  The best-known novels are in a series that begins with the enormously popular Chronicles of the Schonberg-Cotta Family.
• Dinah Mulock Craik.  Not as theological as the others on this list; creates some complex characters and reasonably sophisticated plots.  John Halifax, Gentleman is the novel everybody knows, but Olive is also interesting, as is A Life for a Life (which I praised with faint damns some time ago). 
• Charles Kingsley.  Kingsley's anti-Catholicism deserves the adjective "squicky" (he's far more overtly obsessed with sex than most of his contemporaries), but it's still the case that the novels themselves feature solid plotting and good dialogue.  (Granted, I have the urge to do violence to Alton Locke.) Alton Locke, Westward Ho! and The Water-Babies are the ones that have survived into the twenty-first century, but there's also Hypatia.
• Eliza Lynn Linton.  An evangelical agnostic, Linton tends to be amusingly (or at least assertively) grouchy (although her antifeminism can make modern readers similarly grouchy...). For Linton in full whack-the-church mode, try The True History of Joshua Davidson.   The Rebel of the Family, which I've not yet read, is in print.  (Do skip The Autobiography of Christopher Kirkland, unless you're very interested in Victorian name-dropping.)
• Anne Manning.  I think "amiable" is probably the best way of describing her style, but she's still perfectly tolerable and not always aggravatingly didactic.  She's also responsible for popularizing the diary novel.  (Brownie points for the "My Last Duchess" joke in Tasso and Leonora.)  Try The Maiden and Married Life of Mary Powell, Afterwards Mrs. Milton or The Household of Sir Thomas More.
• John Henry Newman.  Well, obviously, he's not primarily a novelist, and Callista--recently blogged at Siris--is not going to be for everybody; Loss and Gain, however, still goes over well (and features some amusing Victorian snark; Newman, unlike some religious novelists I can think of, actually was in the verifiable possession of a sense of humor.) 
• Charlotte Yonge.  Of the authors who tend to cross my research path, Yonge and Kingsley are the most famous today.  Start with the Heir of Redclyffe, which is still what they call a "good read."