Looking through some old notes of mine, I found the following suggestions for a Gothic book club. Of course, this is just the beginning...
Austen, Jane. Northanger Abbey (1817). The Scream of Gothic novels, in which the characters are aware of all the Gothic conventions even as the heroine lives out, well, something of a Gothic scenario. Light and fluffy, excellent to read after a few heavier works.
Lamb, Caroline. Glenarvon (1816). Often described as "unreadable," but I sped through it in a few days. Apparently, even the trashy novels of previous centuries were on the average better-written than the trashy novels of today.
Le Fanu, J. Sheridan. Uncle Silas (1865). I just can't recommend this book, which I've often described as "the Gone With the Wind of Gothic literature," highly enough. Go read it right now! Also, the Dover collection Green Tea and Other Stories contains most of his classic short stories, with the sad exception of "Schalken the Painter."
Poe, Edgar Allan. Not my fave: I tend to think that Poe's excesses are exactly what people mistakenly think Romanticism's all about. But I do have a soft spot for his "demon woman" stories, especially the one-of-a-kind "Berenice" (1835), which is available in most collections.
Radcliffe, Ann. The Italian. (1797) Even though The Mysteries of Udolpho is the most famous of her works, and the one you need to read to get the jokes in Northanger Abbey, I more highly recommend this novel as a starting point. If you enjoy it, then by all means, read Udolpho as well.
Richardson, Samuel. Clarissa (1748). Not, strictly speaking, a Gothic, but with its innocent heroine, seductive, Satanic anti-hero and intense claustrophobia, definitely a forerunner. If the Austen canon makes you flinch, you're unlikely to get through this books' 1000-some pages. If not, and you're willing to be swept away, it's one of the greats. However, don't try to read a condensed version. The much shorter version is also much more boring, one of literature's strange paradoxes.
Rymer, James Malcom. Varney the Vampire (1845). No one will ever mistake this for great literature, but heck, I've read Dean Koontz's best-selling Shadows, and if that book's clunky dialogue, unrealistic situations and inane digressions don't trouble modern readers, neither should Varney's. It's also interesting in that its core of character relationships--innocent young woman attacked in her bedroom, with a diverse group of men who vow to protect her and track down the monster--is a precursor to the similar dynamic in Dracula. Even more interesting, the familiar relationship of suave, well-dressed, aristocratic vampire in love with his prospective victim--later seen in Dark Shadows and the non-faithful adaptations of Dracula in the 1970s and the 1990s--seems to have started with this book.
Stoker, Bram. Dracula (1897). Of all the vampire books ever written, there's a reason why this is the big daddy. Its prosaic obsession with the latest technology grounds it in modern literary realism, and that contrast makes the breath-taking eroticism of the vampire attacks stand out all the more.