For one thing, this isn't really a book about Tolkien; he's a minor character in a sub-plot who has less presence here than the book's subtitle wd lead you to think. Instead, this book has three distinct strands, of which Tolkien features in only one (with a cameo in another).
(I) First off, there's the main story, what we may call the DaVinci Code thread: a Dan-Brown style modern-day mystery about a woman trying to find her missing grandfather and make sense of the pile of old manuscripts he left behind; she's trying to sell the movie rights to these (to a Hollywood exec. who likes to put Peter Jackson on hold but implausibly always has time to take her calls), while staying ahead of the Bad Guys. Said Bad Guys include a Shelob-spider laired in an abandoned subway station, various Corporate Suits, and most of all a Wraith in Manhattan who impersonates first DiNiro's character from TAXI DRIVER before shifting to Alan Rickman's character from DIE HARD. Luckily for the plot, the Dark Lord's unstoppable assassins are almost comically inept: the one sent after her granddad fails when the old man escapes by outrunning him after having been stabbed in the leg (in a scene reminiscent of one from Dunsany's UP IN THE HILLS), while the one sent to kill our heroine shadows her in various disguises for days, glorying in his ability to kill her any second, yet is more like a Gilbert-&-Sullivan policeman who never does quite get around to doing the job.
(II) Second, there's what I think of as the Notions Club thread: brief alternating chapters of transcripts from audiotapes of Inklings meeting (and yes, that's just as unlikely as it sounds) in which Tolkien explains (pontificates) to his fellow Inklings (Clive, Charles, Owen, Ian, Cecil, Jack, Richard, Ansel) his goals and sources for writing LotR. Here's where a novelist has the advantage of the scholar: in THE HISTORY OF 'THE HOBBIT' I spent pages discussing THE DENHAM TRACTS and the possibility whether Tolkien was or was not aware of the occurrence of the word 'hobbit' in them, whereas Hillard simply has his character 'Tolkien' say "I borrowed . . . 'hobbit' from a list of imaginary creatures in the Denham Tracts" [p.126]. Probably wrong, but so much easier to deal with in a fictional world than our own!
The problem with this thread is that Hillard isn't at all interested in portraying Tolkien as he actually was; his 'Tolkien' is a fictional character only vaguely resembling the real person. Thus he feels no compunction about making the details of his fictional Tolkien's life match up with those of the real-life figure -- to give a single early example, in his bizarre opening scene in which Tolkien arrives in a New York airport in 1970, Hillard has him feeling fear "for the first time since he was eighteen at the Battle of the Somme" [p.2]. The big issue here is that flying, for the first time, by himself, to New York, when he was almost eighty is something that wd never happen in a million years.* The small-focus detail is that Tolkien was born in 1892 and the Somme (the worst battle in history, in which Tolkien did take part) was in 1916, when he was twenty-four. If you're nit-picky about details -- and a great many Tolkien fans are, famously -- then you'll probably find Hillard's disregard of such facts annoying. If, on the other hand, you don't know much about Tolkien you won't mind -- but in that case, why wd you be reading "A Novel About J R R Tolkien" anyway?
It's pedantic to focus too much on inaccuracies in what is after all a work of fiction. But the underlying point is that Hillard doesn't know as much about Tolkien as most of his readers do, which makes for an odd disconnect. The details are just an outward sign that Hillard's Tolkien says and does whatever the plot needs him to, with no regard for the original JRRT's personality or history. With a less well known figure, it's easier to get away with giving his or her fictional analogue a personality and history unlike the real person's -- e.g., Orson Scott Card's delightful and totally bogus "William Blake" in the Alvin Maker series. But Card's book wasn't billed as "A Novel About Wm Blake" or targeted at Blake scholars; had he done so, that wd have raised certain expectations, only to dash them. So with Hillard.
To be fair, I'm not sure how much this 'Tolkien'-is-not-Tolkien element wd bother some readers; it's become something of a pet peeve with me to have fictional characters based on real-world figures who wildly diverge from their original's personalities. I see it in stories about Poe all the time, but the most egregious example I know of is Thomas Wheeler's THE ARCANUM , in which Arthur Conan Doyle is clever like Holmes rather than gullible as in real life, Houdini is respectful of Doyle's beliefs regarding the supernatural, and Lovecraft (a notorious xenophobic) has a hot romance with a black Voodoo Queen. On the other hand, my friend Monte (hi, Monte) said apropos of this that if he were to read a story about a historical character, he'd want that person to be as we imagine him rather than as he really was -- e.g. Doyle as a real-life Holmes rather than the muddle-headed old duffer he really was. That's a valid point, so perhaps it's best to fall back on 'Your Mileage May Vary' here.
(III) Third and last, there's the Betty-Sue Hobbit Saves-Middle-Earth thread: Most of the action of the main (DaVinci-Code-ish) plotline consists of sitting down and reading new installments of the story contained in the bagful of ancient manuscripts and scrolls. Hillard, who says [Dedications page] he was inspired to write the work when his daughters asked "So, where are the heroines?" after being read THE LORD OF THE RINGS aloud, posits that Gandalf, being a misogynist,** ripped out all the pages in THE RED BOOK OF WESTMARCH relating to one of the major characters in the Quest of the Ring: Aragranessa (Ara) the Hobbitess, the RingBearer's lover (Frodo being here called "Amon" for some reason). The imbedded story, a translation of these discarded pages and similar scraps, tells how Ara, realizing that the Quest will prove the death of the Bearer, sets out on her own quest to help out -- during the course of which she gets captured by the Black Riders at Bree (making her the Odo of this Alternative LotR), witnesses the Dark Lord eliminating some annoying envoys in person (a portrayal of Sauron even weirder than John Boorman's Sauron-as-Mick-Jagger, which I had not hitherto believed possible), finds the Valley of the Entwives, wanders about in Mirkwood a lot, visits the kingdom of blase aesthetes, and arrives at Mount Fume (=Mt Doom) just as the Bearer (Frodo) is climbing up from another direction. She and her lover destroy the Dark Lord together, with the Bearer (Frodo) dropping Bind (the Ring) into Mount Fume (Doom) at the same time as she does the more important task of tipping over the Dark Lord's infernal device and spilling the earth-juice ("The Source") that's the true source of (Sauron's) powers. In the end she and (Frodo) shack up together happily ever after; he stays with her instead of sailing away across the Sea.
It'd been said that this book had been the target of a cease-and-desist order from the Estate because it featured Tolkien as a character, which made no kind of sense at all -- live authors can sue for libel about the way they're portrayed as characters, but dead authors are fair game (much more than the characters created by those authors, in fact, odd as that may seem). Besides, there's been ample if unillustrious precedent in Jeschke's various Xian-fiction books featuring Tolkien as a minor character, or James Owen's rather weird take on Tolkien, Lewis, and Wms as epic adventurers through the worlds of Story, or more recently Downing's LOOKING FOR THE KING, all of which feature Tolkien as a character, the latter two at least as much if not more than Hillard does.
No, what I think the cease-and-desist is about (assuming one was ever sent -- not everybody who cries Lawyers! has actually seen one, as per The Boy Who Cried Wolf) was not the chapters depicting Tolkien and the Inklings but Hillard's attempt to re-write THE LORD OF THE RINGS as "ARA'S TALE, OR THE HOBBITESS". Hillard uses Tolkien's setting, his plot, his characters, his world, and his races, simply hiding the names under transparent equivalencies ("Dark Lord" rather than "Sauron", "Bearer" rather than "Ring-Bearer", "Fume" rather than "Mount Doom", "Bind" instead of One-Ring-To-Bind-Them-All, &c). Fan-fiction re-writes or riffs off of famous stories all the time, of course -- e.g., STIFF UPPER LIP, BILBO -- but that's a good-natured exercise that doesn't aspire to being treated like formally published fiction. I found Hillard's procedure more egregious even than Dennis McKiernan's, in that McKiernan shamelessly produced a sequel to Tolkien's tale, changing the names around a little, and then a prequel to the sequel that's a re-writing of T's original, but at least showed that he enjoyed and admired JRRT's tale, whereas Hillard explicitly condemns Tolkien's story as sexist and sets out to 'fix' it.
But Hillard is no J. R. R. Tolkien. He's not even Dan Brown. Ara's tale, when it's finally recovered, turns out not to be up to the level of THE VERY SECRET DIARIES, or even FUNGO HALFWISE. It's a story about Middle-earth by someone who seems not to like Middle-earth v. much; a novel about Tolkien by someone who doesn't know much about Tolkien; an imbedded fiction that neither works as homage nor corrective. Hillard doesn't give us much reason to care what happens to Ara, and even less to like Cadence, his main character in the modern-day frame story; the only really sympathetic character is Osley, the burn-out-case street-person (former research assistant to JRRT) she finds to do all the translating from the Elvish for her.
In fact, the impression I took away from reading the book is that Hillard doesn't really like Tolkien that much but was just using him as a springboard to launch the series, the subsequent books of which look not to have anything to do w. Middle-earth at all (cf. the teaser for the projected second book on p.467). This dismissive attitude towards Tolkien himself makes him out to be nothing more than the lucky recipient and transcriber of ancient scrolls, ignoring all the years of work and unique creative imagination he used to actually create his fictional world -- and that's what really upsets me most about the tack Hillard has taken.
So, not a book I expect to read again. Too bad.
*Hillard similarly described The Algonquin as the Inklings' favorite hotel, not because any of them ever stayed there but because he wants to bring Dorothy Parker's famed hang-out into the story for some reason. The only Inklings I know for sure ever came to America are Havard, Warnie, Barfield, and of course Christopher Tolkien; neither Wms nor Lewis nor JRRT ever made the trip.
**much later it's suggested that The Dark Elves wrote sinister runes on some of the vellum/parchment pages among the cache, then erased them, so this evil palimpsest wd be activated if anyone ever read the story overwritten on these pages -- but this explanation wdn't apply to pages within the Red Book itself, you'd think. For Hillard, these Dark Elves are far more important as a threat than the Dark Lord himself, who it's suggested is merely one of their many dupes.