The only authoritative text based on the complete original manuscript of "Huckleberry Finn" hits bookstores this month. It is the product of painstaking research by the Mark Twain Project at UC Berkeley's Bancroft Library that began shortly after the manuscript's first half was uncovered in a Hollywood attic in1990.

The book rewards readers with new and ample information to help answer questions that have perplexed "Huckleberry Finn" fans and to present enough new ironies to intrigue them all over again.

"I think there's a whole lot that's new here," said Lin Salamo, one of the book's editors.

"Huckleberry Finn" is not just a humorous good story about a charming American bad boy from the idyllic pre-Civil War days, his friendship with a runaway slave and battles with his conscience. The book is considered Twain's best work, as well as a compelling commentary of American race relations, class and violence that is as provocative today as when published in 1885.

The book's popularity continues, as witnessed by the more than 100 editions of the book in more than 53 languages and its presence not only in books around the world but on CD, audiotape and e-book.

"One hundred and fifteen years after its publication, critics and scholars are still scouring the book for what is real - for clues to the actual counterparts of its fiction - attempting somehow to grasp the essence of what it says about American history and culture," editors of the latest "Huckleberry Finn" write in its foreword.

Editors Salamo and Victor Fischer, who worked with Harriet Elinor Smith and the late Walter Blair, have explored the original manuscript, scholarly critiques of the book, Twain's notebooks, speeches, letters, essays and interviews. They compare and contrast them with popular songs and cultural practices, hymns, Biblical references, obituary poetry and even ad slogans of the era.

The layers and layers of information about Twain and the book are presented "not so you're led by the hand, but so that you're given the tools to make an interpretation," said Fischer. "You can mine this novel for so much cultural and historical information that is still relevant today. And we can now answer questions that we never could before we had access to the entire manuscript."

When did Twain, for example, really begin writing "Huckleberry Finn?" The answer: 1876. He handed over a final, typed manuscript to the typesetter in 1884.

By following his work on types of stationery that he used at different times, and tracing his writing medium as it ranged from black ink to purple and blue ink to pencil, the editors pinpointed the three periods during which Twain wrote various portions of the novel.

No, the editors concluded, Twain did not - as long thought - pigeonhole the manuscript after Chapter 16 and the steamboat crash. He actually wrote two more chapters, and then he did put the book aside - for about three years - and then again for another three years, taking seven years to finish it.

Editors of the book published by the University of California Press are excited to show side-by-side for the first time Twain's earliest draft and his final revisions and to show how his most famous characters and story evolved. Each half of the manuscript contains more than 1,700 revisions by the author, with 88 percent of them reflected in word changes, spelling, punctuation and emphasis, the editors report.

"We have a database that analyzes every word he used," said Salamo.

This "library edition," designed mainly for the general reader and for the classroom, updates the Mark Twain Project's 1985 version of "Huckleberry Finn" in numerous ways:

* It includes facsimiles of 16 key pages of the manuscript that show crucial moments in the book's composition.

* It also contains three passages from the manuscript that do not appear in the book in the same form, if at all. One is a ghost story omitted from the book. Another is Huck Finn's description of sunrise on the river, which indicates dramatic changes after the manuscript, and a third passage about a camp meeting that underwent substantial rewriting on the original page, and still more before the book's printing.

* There also is a glossary of terms, notes and almost 40 pages of reference citations ranging from "Arabian Nights" and H.L. Mencken to Robert Louis Stevenson and Noah Webster.

* It also includes all 174 first-edition pen and ink illustrations by young cartoonist Edward Windsor Kemble, artwork generally left out of most contemporary editions of "Huckleberry Finn."

* The latest edition also features new maps of the Mississippi that help readers navigate Huck Finn's journey.

* The book also shows that "break dancing" was popular in the pre-Civil War days and adapted from African dances.

* Kemble's drawing of Huck and Jim's first encounter shows Jim on his one knee, hat in hand. Far from a demeaning depiction of the runaway slave, the sketch is almost identical to a widely known graphic symbol of the campaign to end slavery.

* Another sketch in the book of Jim's "coat of arms" - a slave figure toting a knapsack over one shoulder and running - is virtually the same as the image commonly used in newspaper notices about runaway slaves.

Solving a primary puzzle, the Twain project team also concluded that, although Twain repeatedly interrupted his writing, the breaks coincided with other pressures or a need to finesse a character or solve a problem with the plot. The new edition of "Huckleberry Finn" traces how Twain developed Huck's sensibility and capacity for articulating his thoughts.

Having the whole manuscript at last made it possible to trace how Twain labored over his story and style and how he learned slowly and through thousands of revisions to develop and transfer Huck's inimitable voice onto the page. These records show him replacing the word "forest" with "woods," "wasn't" with "warn't" and "the whole world was dead asleep" with "the whole world was asleep, only sometimes the bull-frogs a-cluttering, maybe."

Kemble's drawing of Huck Finn and runaway slave Jim, drifting down the Mississippi River on a raft, graces the cover. The book is dedicated to teachers who continue to make "Huckleberry Finn" a welcome guest in their classrooms.

Twain scholars already are raving about the new work.

Louis J. Budd, author of "Our Mark Twain" and "Mark Twain: The Contemporary Reviews," said that, due to the UC Berkeley research, "we now have the genome filled in for 'Adventures of Huckleberry Finn.'"

Shelley Fishkin, editor of "The Oxford Mark Twain," and "Was Huck Finn Black?" said the "ingenious textual detective work rescues Twain at last from hundreds of careless errors by typists, typesetters and proofreaders."

The Mark Twain Project houses the world's largest collection of manuscripts, letters and notebooks of author Samuel Clemens, who wrote under the pen name of Mark Twain. The project aims to publish 70 authoritative editions of his work by the year 2010, the 100th anniversary of the writer's death.