I refer you to *The Necronomicon Files: The Truth Behind the Legend,* by Daniel Harms and John Wisdom Gonce, III.
Nightshade Books, 1998. In the chapter titled: "Many a Quaint and Curious Volume: The Necronomicon Made Flesh," Harms lists the following Necronomicon hoaxes/jokes/fan labors of love:
The Faraday Review: Although Harms could not track down a copy of the paper in question, correspondence and other papers indicate that Donald A. Wollheim, at some point in the early 1930s, submitted to a small town Connecticut newspaper a review of a new English translation of the Necronomicon by one W.T. Faraday. This was supposed to be the second publication since the Wormius edition and "only a third as long as the original, as the translator excised the manuscript 'for safety's sake.'" The translation itself, of course, never existed.
Cultus Maleficarum (The Sussex Manuscript), by Fred Pelton. Pelton was an active fan and based his "translation" on both Lovecraft and the more dualistic Derleth version of the mythos. Pelton was a very serous fanboy indeed, going so far as to create an illuminated leather-bound copy, which Derleth actually considered for publication at Arkham House. Although the location of the original manuscript is unknown, Edward P. Berglund obtained a photocopy for publication in his fanzine *Crypt of Cthulhu.*
The Necronomicon for Sale
Ads advertising or requesting copies of the Necronomicon have appeared in various bibliophile magazines; the ads have been hoaxes, but some of the requests are undoubtedly genuine, people being what they are.
Druillet's Leaves from the Necronomicon
Philippe Druillet, a French illustrator, published plates of "pages from the Necronomicon" in a magazine called Anubis and a special Lovecraft-themed issue of Heavy Metal. "The pages themselves are unreadable, but feature a great deal of mystical-looking calligraphy and sketches of alien monsters with bat-wings and inhuman faces." A promised "complete" book never materialized, but the pages have floated around the net.
The Necronomicon: A Study
1967 - a book-length edition from Jack Chalker's Mirage Press, Baltimore. "The book is usually listed under Mark Owings' name in catalogs, but I have been informed that Owings researched the book and Chalker wrote it and then published it under special arrangement with Arkham House." This was a limited edition of 600 copies, and includes Lovecraft's essay "History and Chronology of the Necronomicon," quotations from the book used in mythos fiction, a bibliography listing all the editions and copies that Owings could document from the stories (including non-Lovecraft material).
De Camp's Al Azif
Owlswick Press, 1973. Technically this should be George Scithers's Al Azif, as he produced the faux-Arabic pages and asked L. Sprague De Camp to provide an introduction, which is suitably exciting. "The pages at beginning and the end of the 'Duriac' manuscript differ widely from each other, but those in the middle repeat a sequence of sixteen pages, half of these differing from the other half only by a few characters at the ends of some lines." Until the mass paperback appeared, this was the Necronomicon you were most likely to run across by accident; and many people persisted in believing it despite the page repetition. (If your cover letter ordering the book hinted that you believed the book was real, Scithers would return your check.)
The Culp Necronomicon
1976, Robert C. Culp, Esoteric Order of Dagon. This fan-produced work is apparently more a story than a grimoire.
H.R. Giger's Necronomicon
1977 - A two-volume art book inspired by the mythos
The Simon Necronomicon
The mass-market paperback.
Harms starts talking about this book on page 61, and continues to p. 67. Later, Gonce - who is a practicing ritual magician - goes on at length about it, labeling it "the Anarchist's Handbook of grimoires." I'm not even going to try to summarize their material, as I have a horse's birthday party to attend and want to finish this entry in time to prepare.
The Hay Necronomicon
Although this book is called the Hay Necronomicon, it's clear that Harms believes the crucial person involved with it is Colin Wilson, with whom I'm sure everyone here is already familiar. It appeared in 1978, and was reprinted in paperback in 1992 by Skoob Esoterica.
Das Necronomicon
Gregor A. Gregorius, Verlag Richard Schikowski, Berlin, 1980. A German translation of the Simon Necronomicon in conjunction with a translation of a genuine medieval grimoire, The Goetia. Gregor A. Gregorius was a pseudonym for Eugen Grosche, head of the German occult group Fraternitas Saturni, a branch of the Ordo Templi Orientalis; however, Grosche died in 1961.
The Carter Necronomicon
Although short stories claimed to be from "the Dee translation" of the Necronomicon appeared during Carter's lifetime, Carter's Necronomicon material was not collected together and published until after his death, first by the fanzine Crypt of Cthulhu and then by Robert M. Price, as discussed in the next entry:
The Price Necronomicon
Chaosium (that's the Call of Cthulhu game people), 1996; those of you who've seen their trade paperback collections will instantly be able to picture this. It collects Mythos stories, the Sussex Manuscript, the Carter Necronomicon, and essays and editorial matter by Robert M. Price, the editor of Crypt of Cthulhu. I can heartily recommend any Chaosium product; but that's neither here nor there.
Black's Necronomicon
A hijacking of the name for the title of a collection from a magazine focusing on Horror and Erotic Cinema.
Necronomicum Novum
John Opsopaus - first appeared in a hard copy 1995 issue of Mythos magazine, since floating around the net; oddly, has more to do with Mediterranean myth than Lovecraft
Other Necronomicons
A rundown of rumors and plea for copies.
And who knows what's been going on since 1998!
So, the short answer is: No, there is no definitive version.