It's really quite hard to know how to review a book like this: the intention is so excellent and the execution so jarring.
For some readers, the purpose of a book like this is simply to allow you to follow the story and say "Hey, look at me! I'm reading real live Latin, and enjoying it!" And it is indeed engaging: the slower pace of reading allows you to notice things which slip by when you are re-reading the English. On this level, it's just a bit of fun: no point in being pompous about it.
Unfortunately, such books are equally likely to be used as a learning aid by those actually studying Latin. In that case there is a serious purpose in these translations: to make the reading easy and enjoyable by using a familiar and much-loved story while at the same time painlessly giving you a feel for how Latin prose actually works. This is where it fails badly. It's not a question of not conforming to some Augustan canon of elegance: misunderstandings, often amounting to howlers, occur on almost every page. I'm not saying I could do better; but I can tell when a table wobbles even though I do not know how to make tables.
The trouble starts on the title page: where _do_ so many English people get the idea that "ille" can be used as the definite article? All right, it is the ancestor of the definite article in most Romance languages, and was legitimately used in "Winnie Ille Pu", but there the idea was to render the extra emphasis in "Winnie THER Pooh". "There and back again" is rendered as "Illuc et rursus retrorsum". "Back again" is an English idiom, which does not exist in Latin. "Rursus retrorsum" is an ugly duplication: etymologically it amounts to "reversus retroversum". The only sensible meaning is that he went back once, and is now going back a second time: not what the book means.
And so it goes on. I agree with all the points made by the previous reviewer (Johan Winge): my thirteen-year-old son, who has been learning Latin for less than a year, fell about laughing when I told him about "tange et i".
The main fault is insensitivity to shades of meaning. For example:
*"foramen" means a perforation in a surface, such as a hole in your sock. It cannot mean a hole in the ground. Even leaving that aside, "foramen-hobbitum" would mean a hole which is a hobbit, not a hole belonging to a hobbit. And there are many further awkward English-style hyphenations and italicizations, which could have been avoided by standard Latin idioms.
*"as your friends may tell you" is translated by "licet", meaning that it is lawful for your friends to tell you. (And "licet" is used this way in several other passages.) It should be "ut potes discere ab amicis" or something similar.
*"facinus" for "adventure" may be just about defensible, but its normal meaning is "crime". (Admittedly, "adventure" here is very hard to translate: a recurrent joke in the original turns on the ambiguity between "adventure" in the sense of a speculative enterprise and "adventure" in the sense of a dangerous thing that happens to you.)
*"rixantem" for "scuffling". Even apart from the participle question, "rixa" means a quarrel with raised voices, with or without a fight. "Scuffle" in English can sometimes mean a fight. But in the original passage, it has its other meaning, of a noise made by a lot of feet.
*"veri simile" for "probable" (several times): can be used for whether someone's account appears believable, but not for whether something is likely to happen in the future, which is how it is usually used here.
*recurrent use of "tempus" to mean "time" in phrases like "another time" and "this time" (should be "hac vice").
*"admirari" for "wonder". Yes it does mean to wonder, in the sense of being amazed. It cannot mean to wonder whether.
*"caput" for "head" in phrases like "lost his head" and "keeping a clear head". "Caput" has several metaphorical uses in Latin, apart from the literal meaning of a part of the body; but it is never used for "mind" or "mental processes".
In other cases there are outright mistakes:
*Bilbo at one point hopes that the dragon is not sitting on the mountain looking down at them. The Latin makes him hope that the dragon IS doing this.
*in that wonderful exchange "little time to lose" /"little food to use", the Latin uses "time" instead of "food"!
*several times a plural noun takes a singular verb, though this may be a proofreading error.
*several uses of a participle to translate an English gerund, and of infinitives to render phrases like "nowhere to be seen".
Literal rendering of idioms:
*"for many a year" and "many a fair elf" are translated by "multus" in the singular. This idiom simply doesn't exist in Latin.
*recurrent use of "unus" for "one" in the sense of a specimen of a previously mentioned class, as in "a burglar, but an honest one". Again, not a Latin usage.
*some proper names are rendered by ridiculous Anglo-Latin compounds like "Mirksilva" and "Arkenlapis".
*the translator cannot decide whether to use "homines" for "human beings" or for "people" in general (including elves and dwarves): in the Tolkien world, a somewhat important distinction!
In short, it reads as if a student has ploughed through translating word for word with the help of a dictionary: of Latinity it has simply none. I can't quite make out how it happened, as the translator clearly knows a great deal of Latin and presumably has plenty of teaching experience, and some of the verses (for example the hendecasyllabic song about the barrels) are excellent.
But don't let me deter you from getting it. All said and done, it is a pleasant read, as nothing can destroy the charm of the original story; and one day it will have value as a collector's curiosity.