Reason Magazine's Jesse Walker, a RAW scholar often mentioned in these posts, reached back to 1800 (last item) when he was asked to name the best book of 2012.
Julia and the Illuminated Baron by Sally Wood is a Gothic novel, apparently in the tradition of Ann Radcliffe, author of 1794's The Mysteries of Udolpho. The original Gothic novel genre is mainly remembered now because of Jane Austen's satire of it in Northinger Abbey.
Jesse explains, "Coming in the wake of the Illuminati panic of 1798, in which Federalists fretted that the secret society was aiming 'to subvert and overturn our holy religion and our free and excellent government,' Wood weds those anxieties to a Gothic melodrama set in pre-revolutionary France, featuring an Illuminatus who holds a young woman captive and plots against her virtue. Wood's Illuminati are a depraved band of nature-worshippers, seizing personal pleasures as they prepare for the Jacobin apocalypse. At one point Wood has a woman describe the order's initiation ceremony: 'disrobed of all coverings except a vest of silver gauze, I am to be exposed to the homage of all the society present upon a marble pedestal placed behind which sacrifices are to be offered.' The character adds, 'This sect increases daily. They will in a few years overturn Europe and lay France in ruins'." (Notice how Jesse, with a keen eye for detail, manages to find what's likely the one salacious sentence in the book.)
Here's an interesting article about how the University of Maine at Machias brought the long-forgotten novel into print.
You likely won't find Julia in your local bookstore, and I couldn't even find it on Amazon. You'll have to follow a link from Jesse's article to buy a copy.
But an Amazon Kindle version is in the works. When I wrote to the "Library of Early Maine Literature" at UMM Press to ask about a Kindle edition, I was told to look for it this summer, maybe fall. I got a follow-up email, however, telling me the new target date is the end of January.