I'm not normally big on writing about half remembered books read six years ago, but there's enough misinformation running around about Shiki I felt the need to try and get things straight somewhere. Shiki is a novel -- not light novel -- by Fuyumi Ono, author of the Twelve Kingdoms books (which were actually light novels. Confusing!) The hardcover edition was two massive volumes, and the bunko edition was FIVE volumes, each of which ran for five hundred odd pages. It took me two months to read (although I was reading other books in between each volume of Shiki to keep myself from getting burned out.)
Fuyumi Ono intended Shiki to be an homage to the Stephen King novel Salem's Lot; the story is essentially a Japanese version of that basic concept. A very old fashioned, traditional Japanese mountain town is plagued by a mystery disease; it eventually transpires that the new residents in town are vampires, and are attempting to convert the entire town in the hopes of creating a safe haven for their kind.
While the story is an ensemble cast, and frequently changes the point of view as different characters play their roles -- I wound up writing down people's names and roles in a massive map scrawled all over the book cover, just trying to keep it all straight -- the two primary characters are the town doctor, and a Buddhist monk who writes surreal fiction in the style of Edogawa Rampo.
The novel is a very slow, creeping dread that takes a thousand pages to even reveal the vampires and goes on for another volume well after the point you'd have expected it to end. Ono's dense, literary prose can be a bit of a slog at times, but incredibly evocative at others, and it's well worth a read if your Japanese is up to it.
It's a very strange choice for a manga and anime adaption. I haven't read the manga, but it's by Ryu Fujisaki. I read the first volume of his Hoshin Engi and found it pretty dull, but at least coherent; I then read his Waq Waq when it ran in Jump and found it completely unintelligible. While his design sense can be extraordinary at times, the flow from panel to panel is gibberish, and he's prone to fits of stylization so extreme you can't even figure out what he intended to depict in individual panels. He's an incredibly poor choice for the material, and the garishly lolita gothed out character designs are about as far removed from the source material as it is possible to be. Judging from the ads from the Shiki anime, and the covers of the manga, he's also shifted the focus to the two high school characters; relatively major characters among the supporting cast, and if the storyline in general were stripped down to just their stories it would probably still be a coherent whole. I'm cautiously voting this as actually a pretty smart move on Fujisaki's part. I'm definitely curious about the Noitamina anime, and hoping they can manage to meld the manga art style to some of what made the original novel work for me, but it's very much an unknown quantity at this stage.