The points of issue
The true first is the Land of Enchantment edition (1985), illustrated by Phil Parks, issued only as a signed limited edition in publisher's cloth slipcase. The signed printing was limited to 250 copies, with a small lettered subset (24 copies, divided among author, artist, and publisher). Large quarto in gilt-decorated cloth with color pictorial jacket and pictorial endpapers.
Is this the true first?
The Land of Enchantment edition (1985) is the true first and contains Koontz's original novel. For the 1987 Berkley edition Koontz revised the original text as Part One and wrote an entirely new Part Two, so the Berkley is an expanded later text, first thus for that expanded version.
Telling it from reprints & book-club editions
There is no book-club edition of the Land of Enchantment limited. The widely available 1987 Berkley paperback is the later expanded text, not the first.
Frequently asked questions
Is my copy of Twilight Eyes a first edition?
Look for these first-edition points: The true first is the Land of Enchantment edition (1985), illustrated by Phil Parks, issued only as a signed limited edition in publisher's cloth slipcase. The signed printing was limited to 250 copies, with a small lettered subset (24 copies, divided among author, artist, and publisher). Large quarto in gilt-decorated cloth with color pictorial jacket and pictorial endpapers.
How do I tell the first printing from a later one?
Check the copyright page for the publisher's first-printing convention and confirm the points above. The Land of Enchantment edition (1985) is the true first and contains Koontz's original novel. For the 1987 Berkley edition Koontz revised the original text as Part One and wrote an entirely new Part Two, so the Berkley is an expanded later text, first thus for that expanded version.
Is the book-club edition the same as the first?
There is no book-club edition of the Land of Enchantment limited. The widely available 1987 Berkley paperback is the later expanded text, not the first.
I have a first edition of Twilight Eyes — what should I do?
If you're clearing books, New Mexico Literacy Project offers free pickup in Albuquerque, any condition, and makes sure collectible copies aren't lost. To sell, see the author's collecting guide. Either way, nothing valuable ends up in a landfill.