Most of these are relatively minor, such as the claim that Tolkien couldn't finish A MIDDLE-ENGLISH VOCABULARY without E. V. Gordon's help, or that the Tolkien-Gordon edition of SIR GAWAIN & THE GREEN KNIGHT set the standard for students of Old English for decades thereafter (it's in Middle English). Some are more problematic, such as the claim that Christopher Wiseman helped Tolkien create his invented languages (news to me, and I shd think unlikely -- at any rate, Wiseman never made any such claim to me). Or Horne's statement that Tolkien felt Lit. students shdn't have to study any philology [p. 84], which is the exact opposite of what Tolkien set out in the syllabus he got enacted at Oxford. And even minor errors add up when you keep making them.
And then there's the problem of focus. Horne spends most of his book on Tolkien's youth, a feature of juvenile and young-adult biographies (which assume the reader mainly wants to know what a famous person was like at their age and a bit thereafter); only about a dozen pages are devoted to the last quarter-century of JRRT's life. And this is a pity, because the latter chapters (regarding the writing of THE HOBBIT, LotR, and afterwards) are much the best part of this book: I suspect that Horne, a Presbyterian minister who's also published a study of the GOSPEL OF MARK, is good at bringing to life a well-known story. Another 'juvenile/young adult' feature is that several of the early chapters begin with fictionalized passages (or, as Horne puts it, scenes to which he's added "imagined conversational details"). There's certainly precedent for this: Carpenter devoted a central chapter in both TOLKIEN: A BIOGRAPHY and THE INKLINGS to a fictional re-creation of a 'day in the life'. But whereas H.C. synthesized information from many sources into a single smooth narrative; Horne just re-tells a single scene. Here's the longest such example, from the beginning to Chapter 3 (1910-1911):
"Watch this, Edith," the teenage boy said to the
pretty girl sitting across from him as he picked up
a sugar lump from the bowl at their table. To any
onlooker, he appeared handsome and athletic -- partially due to
a hearty commitment to playing rugby with his schoolmates.
But there were no onlookers here on the second floor.
The couple's favorite Birmingham tea shop had a balcony
overlooking the street below. From there they sat and sipped
tea and watched the foot traffic beneath them, talking of trivial
The boy was too mischievous to merely watch. He had
just spotted a large, flowery hat parading below. It presented
a tempting target for a teenage boy who wanted to impress
a girl. "Don't do it, Ronald." said Edith, in a tone that did
nothing to make Tolkien hesitate in executing his plan. He
gently tossed the lump of sugar at the wide brim passing on
"Oh no," whispered Edith, ducking back behind the bal-
But she didn't need to worry. The sugar lump hit the street
silently, and neither the woman underneath the hat nor anyone
else near her noticed it. Tolkien grabbed another fast, before the
hat was out of range. "This time I'll make it."
He reached his target. Tolkien grinned and Edith giggled as
the lady walked away with an extra sugar lump decorating the
brim of her colorful hat.
"My turn," said Edith . . .
[Horne, pages 26-27]
Harmless enough, but is it really worth devoted almost two pages out of such a brief book (only 130 pages of text before the endnotes & recommended reading)?
Oddly enough, for a book written by a pastor and published as part of a series called 'Christian Encounters', there's relatively little on religion in this book -- certainly no more than in Carpenter, and I'd say probably less.* Although there is one strange passage [p. 12] where the author suddenly denounces Unitarianism; in a podcast interview about his book** Horne speculates that Tolkien's mother appointed Fr. Francis her sons' guardian to keep them out of the hands of the "non-Xian influence" (!) of old John Suffield, their grandfather -- which seems to be overstating things. Horne also has theories about a strong corrolation between creative people and being orphaned, which he brings up twice [p. 6 & p. 17] but unfortunately muddles his math when trying to explain.
Finally, it turns out Horne has his own Tolkien blog, which is well worth checking out:***
In addition to this biography and the book on MARK, he's also written WHY BAPTIZE BABIES, co-authored UNNATURAL AFFECTIONS and a work rather alarming titled HOW TO KEEP THEM FROM TAKING YOUR CHILDREN AWAY, and contributed to A FAITH THAT IS NEVER ALONE, which is a response to 'the Westminster Seminary', whatever that is.
On the whole, I have to say that if you're only going to read one book about Tolkien, you should read Carpenter. But having read Horne's little biography, I think he shows enough flashes of insight that I find myself hoping that rather than another book he'll write some stand-alone essays on various Tolkienian topics.
current reading: THE MAN IN THE MOONE by Francis Godwin 
*but then Bishop Carpenter's son was interested in religion, if not particularly sympathetic to it.
**podcast link: http://trinitytalkradio.com/2010/05/life-of-tolkien/
***although be warned; he seems to be something of a Creationist, if you'd find that a sticking point.
****disclaimer: Horne does cite me in one footnote (regarding the corrected dating of Tolkien's letter about Sam Gamgee), though he doesn't mention my name [Note 8 to Chapter 4, pages 134-135]