If I am talking about a book which has the definite or indefinite article at the beginning of its title, I will always drop it where there are modifiers. I tend to pay no intention to whether it is simply a name for the work (The Iliad) or the name or title of somebody in the book, used as the book's title (The Lord of the Rings). In English, Homer's first epic is called The Iliad, a work which even a typhlochiist* like myself acknowledges shows source material from wide stretches of space and time. So one might talk about "an older Iliad " I would never say "a shorter The Iliad ", nor "Homer's The Iliad"; I would avoid "Shakespeare's A Midsummer Night's Dream".
Adam Roberts has just published an extract from his new book The Riddles of The Hobbit at tor.com. It looks very interesting although I do tend to think that Tolkien scholarship begins with Christopher Tolkien and ends with T. A. Shippey.†
But there is another The Hobbit; a second The Hobbit written by Tolkien, comprising revisions to this first edition, additional material written forThe Lord of the Rings and the appendices of The Lord of the Rings, plus other material. The most significant of these latter are two separate prose pieces, both called ‘The Quest for Erebor’ first collected in the posthumously-publishedUnfinished Tales (1980). Tolkien’s first revisions were confined to the ‘Riddles in the Dark’ chapter. After writing the first Hobbit Tolkien came to the conclusion that ‘the Ring’ was more than just a magic ring conferring invisibility on its wearer—that it was indeed the most powerful artefact in the whole world, one with which people could become so besotted as to lose their souls. Gollum, he reasoned, would not freely give up such an item. So he rewrote the scene, and all subsequent editions of the novel treat the encounter in a less light-hearted manner. This is symptomatic of something larger, a reconceptualising (Tolkien purists might say: a distillation or focusing) of his now-celebrated legendarium. No longer a folk-story, it now becomes a grand sacramental drama of incarnation, atonement and redemption.
"another The Hobbit ; a second The Hobbit " – aaargh! But later he has "After writing the first Hobbit".
Still looks good though.
*In the Hymn to Apollo, traditionally attributed to Homer (hence "Homeric Hymns") , the bard asks the maidens of Delos who is the sweetest singer. They reply that "he is a blind man and lives on rocky Chios". This is the origin of the tradition that Homer was blind and from Chios. τυφλὸς ἀνήρ, οἰκεῖ δὲ Χίῳ ἔνι παιπαλοέσσῃ – typhlos anēr, oikei de Chiō eni paipaloessē.
†You can include his Author of the Century if you like but it is simply a rehash of the earlier book.