Longmont's Dan Simmons refuses to stick to a single genre; in fact, it's hard to find a type of fiction at which he has not excelled.

He may be best known for his Hugo Award winning far-future science fiction tetralogy, which includes Hyperion, Fall of Hyperion, Endymion and Rise of Endymion. But he is equally at home with horror novels like Carrion Comfort, Summer of Night and A Winter Haunting, and detective stories with his Joe Kurtz series.

Regardless of plot or theme, the three elements that best define Simmons' works are his thorough research, literate writing style and celebration of major authors and works of literature.

It's no coincidence that the Hyperion novels make use of the works of Geoffrey Chaucer and John Keats, nor that Ernest Hemingway is a central character in his suspense novel, The Crook Factory. Last year's The Terror, which chronicled an ill-fated 19th-century attempt to find the Northwest Passage through Canada, made significant use of Edgar Allan Poe's The Masque of the Red Death.

Now the erudite Simmons uses one of the greatest novelists of all time as a character and another important Victorian author as narrator in his latest "magnum opus," Drood, as he recounts the last five years of Charles Dickens' life and the mysterious circumstances around the writing of The Mystery of Edwin Drood, Dickens' unfinished last novel.

Chapter One opens as the narrator, now estranged from his friendship with the "Inimitable," as he calls Dickens, introduces himself and his book: "My name is Wilkie Collins and my guess, since I plan to delay the publication of this document for at least a century and a quarter beyond the date of my demise (1889), is that you do not recognize my name . . . Even so, I would wager my current fortune, such as it is, and all future royalties from my plays and novels, such as they may be, on the fact that you do remember the name and books and plays and invented characters of my friend and former collaborator, a certain Charles Dickens."

While it is certainly true that Dickens will never be forgotten, Collins might have been surprised that his most famous book, The Moonstone, is considered by many the first true detective novel and that it is still in print today, or that his The Woman in White would be adapted as a musical by Andrew Lloyd Webber, though the play closed after a short run on Broadway last year.

In just a few pages, the actual story begins with a seminal event in Dickens' life. In 1865 the author, who had separated from his wife, Catherine, the mother of his 10 children, was traveling by rail with the beautiful and much younger actress, Ellen Ternan, when the train jumped the track, and most of the passenger cars plunged into a ravine. Though their first-class carriage was tilting over the edge of a precipice, Dickens and Ternan were relatively uninjured, but the majority of the other travelers died or were seriously maimed in the wreckage.

As he later told Collins, when Dickens worked his way down the hill to help the victims, he met the man, "if he was a man," who would change his life, a cadaverously thin person who appeared to have no eyelids and introduced himself only as "Drood."

As Dickens tries to minister to the horribly mangled passengers trapped in their splintered cars, it appears that Drood, like a vampire, is sucking out their last breaths.

After he has somewhat recovered from the experience (though the author retains a phobia of trains and fast-moving conveyances until his death), Dickens becomes obsessed with finding Drood, and he enlists Collins, his friend, sometime collaborator and the brother of his son-in- law, to accompany him into the slums and London's "Undertown," a secret society, hidden along the subterranean sewers and rivers of the city. Clues divulged by Dickens' acquaintances from Scotland Yard and private detective agencies lead him to believe that Drood lives as a type of potentate in these vast catacombs.

Gradually we learn that both Collins and Dickens suffer from gout, a common upper- class affliction of the times, and that the narrator is hopelessly addicted to laudanum, a combination of opium and alcohol used to treat a multitude of painful conditions. Collins ingests the drug in such copious quantities that we must wonder just how much of what he relates is truth and how much is hallucination.

It is possible that Drood is merely a figment of Dickens' imagination - or Collins'; or he may be part of a story Dickens is creating for his own amusement. He may actually be a serial killer responsible for at least 300 grisly murders. He may be the leader of a possible insurrection by London's miserable lower classes, who will eventually rise up and take over the city. Dickens himself may be a murderer who descends into these pits of depravity as part of a nefarious scheme. And Collins admits that he not only has committed murder, but that he plans to kill his former friend and dump his body in a lime pit.

As Collins continues his "memoir," he frequently strays from the narrative to discuss his own and Dickens' current works, their intimate lives, Dickens' Christmas parties, the "Inimitable's" reading tours, and the life and times of Victorian England and America. For the most part these departures do not detract from the story. However, if there's a criticism, it's that the tale tends to drag a bit.

Fans of Simmons' early work will find the underbelly of London described much as the poor sections of India were in his first novel, The Song of Kali. And early in Drood, there is much discussion of The Frozen Deep, a play on which Collins and Dickens collaborated, that tells the story of the expedition Simmons wrote about in his most recent novel, The Terror.

For those who wish to pigeonhole Drood into a genre, it's safe to say that it is a historical novel, a biographical novel, a horror novel, a mystery, a romance, a Gothic novel, a science fiction novel (since we are supposed to be reading it five years from now), a work of mainstream fiction and a book of literary criticism. Put it on any shelf in the bookstore and it fits.

Mark Graham is a retired high school English teacher. He reviews Unreal Worlds titles regularly for the Rocky.

Drood

* By Dan Simmons. Little, Brown, 784 pages, $26.99.

* Grade: A-