The late Douglas Adams' unstoppably popular 1979 novel, "The Hitchhiker's Guide to the Galaxy" (HG2G), is about, among other things, "The Hitchhiker's Guide to the Galaxy," "one of the most remarkable books ever to come out of the great publishing corporations of Ursa Minor," an idiosyncratic interstellar how-to for those interested in hitching rides on spaceships and generally surviving on 30 Altairian dollars a day. What does it mean when a book about an extraordinary book itself becomes an extraordinary book?

The astonishing success of Adams' novel is both understandable and surprising. (How astonishing? Try 20 million copies astonishing.) He based the first two books (the second is the even better "The Restaurant at the End of the Universe," published a year later) on his successful BBC radio series, and there's something about that medium's disembodied vocalizing that gets carried over into the text, a voice-of-god vibe that allows for gently ironic, smoothly cosmicomic zoom-outs that comment on and complement the various adventures of its main characters: Arthur Dent (seemingly the sole human to survive the destruction of Earth), Ford Prefect ("roving researcher" for the "Guide"), Zaphod Beeblebrox (two-headed, triple-armed president of the galaxy and all-around spaced-out sybarite) and Trillian (née Tricia McMillan, the other persevering homo sapien).

Adding to the addictive fun is the "Jabberwocky" approach to alien names and linguistics (most potently in the sample of Vogon poetry -- the third worst in the universe), and last but not least Adams' uncanny ability to mint T-shirt-ready phrases, dream up unforgettable metaphors: The Babel fish (a creature that, when put in the ear, allows you to understand any language, as the thing feeds off incoming brain waves and excretes information into your brain); "Don't panic" (the HG2G's motto); the importance of carrying a towel; the cosmic import of the phrase "We apologize for the inconvenience"; 42 (the surprisingly terse answer to the meaning of life, the universe, and everything); Deep Thought (the supercomputer built to calculate the question to the meaning of life, the universe, and everything); and a handful more.

I love how the description of the Guide itself, 30 years on, sounds infinitely less fantastic:

"[Ford Prefect] had a device that looked rather like a largish electronic calculator. This had about a hundred tiny flat press buttons and a screen about four inches square on which any one of a million 'pages' could be summoned at a moment's notice. It looked insanely complicated, and this was one of the reasons why the snug plastic cover it fitted into had the words DON'T PANIC printed on it in large friendly letters. . . . The reason why it was published in the form of a micron sub meson electronic component is that if it were printed in normal book form, an interstellar hitchhiker would require several inconveniently large buildings to carry it around in."

This description, written back when a line about humans being "so amazingly primitive they still think digital watches are a pretty neat idea" would feel au courant, now easily conjures a hand-held device, something like a Kindle crossed with a Blackberry.

Eoin Colfer's slackly titled "And Another Thing . . . " (Hyperion: 276 pp., $25.99) is the authorized continuation of the series. In theory, it's altogether fitting that the so-called Hitchhiker's Trilogy, which had self-consciously overflowed to five titles by the time of Adams' sudden death in 2001, should live on. After all, nothing is impossible in the HG2G universe. Death and destruction need not be permanent: The titular eatery in "The Restaurant at the End of the Universe" is "built on the future remains of an eventually ruined planet . . . projected forward in time to the precise moment of the End of the Universe" -- the ultimate dining experience, at once unique and endlessly repeated.

But whereas Adams could make the verb tenses involved with the restaurant's existence a cause for laughter-induced panting, Colfer starts his installment promisingly but ultimately can't match Adams' brilliant insouciance or his knack for memorable inventions.

It's a tall order, of course, and Colfer, author of the "Artemis Fowl" books, tries hard to keep the atmosphere antic. A welcome off-the-cuffness greets the skeptical Earthbound reader, returning to this fictional world after many years. (The last Hitchhiker book Adams wrote, "Mostly Harmless," came out 17 years ago.) Colfer frames "And Another Thing . . . " by asking the reader to imagine scrolling through the legendary "Guide," now equipped with all sorts of audiovisual bells and whistles, and then clicking onto the text-only appendix. "This is the story of that appendix," he writes, in a nice anticlimactic flourish.

But as this book wore on, I started to question not only the whole idea of having another hand (albeit a game and successful-in-his-own-right one) adding to the universe of a beloved author, but also why the parties involved didn't think, as it were, outside of the book.

"Mostly Harmless" was published well before the advent of e-books, and while I'm as anxious about this new technology as the next paste-and-paper devotee, I can't help but wonder whether Douglas Adams, the technophile, would have tried to utilize the electronic platform to reimagine what a book -- specifically, a Hitchhiker book -- could be. (Among other medium-bending exploits, Adams authored an Infocom text-game version of HG2G, as well as a more complex computer game called Starship Titanic, which I still don't quite understand.)

"And Another Thing . . . " punctuates its increasingly tedious story line with entries from the "Guide," some of which show a glimmer of Adams-like spark. What if Colfer had let Arthur, Zaphod and company rest in peace and, instead, given us some approximation of the "Guide" itself? Rather than follow the pesky rules of plot, Colfer might have created something truly anarchic, in the spirit of the original, but in a form Adams could only dream of.

A book consisting only of discrete entries might sound daunting, but, in fact, the structure would be liberating. And any time the reader got confused, a button could be depressed, and those two beautiful words -- DON'T PANIC! -- would come swimming out of the e-ink ether.

Park is a founding editor of the Believer and the author of the novel "Personal Days." Astral Weeks appears monthly at latimes.com/books.