''Cloud Atlas'' has already been published in England. On the other hand, what Mitchell is doing is basically James Michener's ''Alaska'' with an I.Q. On one hand, Mitchell's strategy is boldly antithetical to what most narrative-driven novels have been up to since Cervantes. With ''Cloud Atlas,'' Mitchell has returned to the rather nutty method of ''Ghostwritten'': the novel gives us six separate stories, spanning the planet, that cover roughly 1,000 years of time. ''Number9Dream,'' his second, largely follows a single character through Tokyo and beyond, but the story fractures along so many stress lines of the possible and impossible - confusion the book does almost nothing to repair - that the novel becomes little more than a beautifully expressed fantasia. The book's meaning is the readerly equivalent of an inkblot test. ''Ghostwritten,'' his first, involves nine characters (a musician, a terrorist, a host-seeking poltergeist and so on) and nine different locales that have no formal connection to one another. The difficulty comes in how Mitchell chooses to construct his novels - or rather, how he does not choose to construct his novels. Mitchell is as good at aphorism (''Faith, the least exclusive club on earth, has the craftiest doorman'') as he is at description (''Now and then goldfish splish and gleam like new pennies dropped in water'').

On the contrary, his prose is straightforward and, quite often, magnificent.

One does not sense that - unlike, say, William Gaddis, Carole Maso or Walter Abish - Mitchell is trying to chop down the tree of literature in order to replace it with something treelike. Mitchell is neither abstrusely arch nor a wizard of scenic dislocation. This is to the good the tree of literature drops its best fruit after being shaken with conviction and intelligence.

Deliberately difficult novels are the only novels he seems to be interested in writing. John Updike's odd (and wonderful) early novel ''The Centaur'' seems to have been written from this impulse, as do Philip Roth's equally bizarre novel ''The Breast,'' Norman Mailer's ''Why Are We in Vietnam?'' and Kazuo Ishiguro's ''Unconsoled.'' Among this crowd, the young British novelist David Mitchell stands out. Some novelists just seem to say, What the hell. It is also not an urge unique to modernism or experimentalism. This urge does not necessarily result in novels with nameless characters, mutating typography or unpunctuated attempts to explore the aphotic realm of human consciousness.

IT is not unheard of for a novelist of exceptional talent to write a deliberately difficult book.

Cloud atlas book explained