Here’s what we know. In June of 1816, Lord Byron, John Polidori (Byron’s personal physician), Percy Bysshe Shelley, Mary Godwin (soon to be Mary Shelley) and Claire Claremont all gathered at Byron’s place on the shore of Lake Geneva, Villa Diodati. 1816 was a “year without a summer” because the year before a huge volcanic eruption had sheathed the planet in a blanket of sun-blocking dust. On what must have been one of many dark and stormy nights that summer, the above-named crew sat around a fire and told stories. (See Ken Russell’s 1986 film Gothic for a wonderfully kinky version of the story of that famous night.) It was so much bone-chilling fun that young Mary (she was not quite nineteen at the time) suggested that they all write supernatural stories. And all agreed.

What followed is history: Mary wrote Frankenstein, Or the Modern Prometheus, the grandmother of all science fiction novels. The rest of the Diodati gang went on to fame or obscurity, as the case may be, but none followed up on Mary’s challenge. Or did they? Polidori, in fact, wrote a short novel called The Vampyre, generally credited with being the first tale of blood-sucking in English. But there’s a controversial line of evidence that strongly indicates that Polidori, more than a bit of a blood-sucking sycophant, stole the idea and plot of The Vampyre from Byron. There’s a scrap of a prose manuscript by Byron on that subject, and it seems likely that Byron, before he told Polidori to hit the road, conveyed to his doctor, in great detail, the nitty-gritty of the vampire tale. So Polidori’s novel, this line of reasoning goes, is really “Lord Byron’s novel.”

Which is what I was expecting when I read Crowley’s latest outing (he’s the author of a number of well-regarded novels, including Aegypt, one of a tetralogy and, before The Evening Land, The Translator). But The Evening Land is not a vampire story at all. The Evening Land is, in fact, two novels, one tucked more or less neatly inside the other (which explains the bulky title).

Lord Byron’s novel is discovered in an enciphered manuscript. (What is it about codes, ciphers and old manuscripts in recent fiction? There’s The Da Vinci Code, of course, but also Caldwell and Thomason’s The Rule of Four, Stephenson’s The Baroque Cycle, Grossman’s Codex, and Phillips’ The Egyptologist, among others; we seem to have entered an era of epistemological uncertainty in fiction, acting, perhaps, as a counterweight to the textual fundamentalisms of a certain Administration’s certainties.) Byron’s daughter, Ada Byron Lovelace, the godmother of modern computer programming is, in Crowley’s novel, the woman who preserves her never-met father’s novel by enciphering it (thus simultaneously defeating and according her mother’s wishes that the manuscript be destroyed).

It’s up to a lesbian couple—a historian who is writing and designing a Web site dedicated to the recovery of the history of women in science and her Aspergeresque math-whiz girlfriend—to decipher the novel. Add to this a more-than-slightly Freudian relationship with the historian’s long-lost father (a filmmaker cum Byron scholar, conveniently enough) and you’ve got the elements of a complex and satisfying yarn with hints of a parallel to Byatt’s Possession. We get the story of the decipherment as a series of e-mails between the girlfriends, while Lord Byron’s novel is presented in, so to speak, plain text.

The novel opens with a long passage from Byron’s novel, the story of Ali Sane, the half-English, half-Albanian son of Lord Sane. We are congratulated by the putative Byron on wading through these first pages; it’s the only part of the novel which nearly lost me. That’s a dangerous burden for a writer to place on his reader, but it turns out to be well worth the wade. Ali is marked with a tattoo that identifies him as the heir of Sane, and he is whisked from the Albanian outback (where his father abandoned him before birth) to the outback of Sane’s green and pleasant land, England. What ensues in Byron’s novel is a tale of murder, lost loves, betrayal, sudden reversals and (gotta love this twist on the Gothic supernatural) zombies.

Crowley does an amazing job of capturing the early nineteenth-century voice of Byron; The Evening Land is full of both subtle and obvious allusions to Byron’s life and work. It’s not hard to imagine that this novel really is a fictionalized autobiography of Byron, who was a champion of marginalized peoples and cultures, and especially of Albania and Greece. (The comparisons to Byron’s life are intriguing, as the characters in the novel-within-the-novel point out to each other; and as well as Possession there is a strong resonance here with Le Carré’s Our Game.) The metanovel, the story of the decipherment of The Evening Land, is perhaps less brilliant: the use of the e-mail format seems, at first, forced, as does the insistent drawing of parallels between the father-daughter relationships of Ada and Lord Byron and the historian and her Byronic father. There’s a bit of wading to be done but once in the reader is in, we’re up to our eyes in a great story full of wit and insight.