Read the book. If you like it, then (and only then) will you be prepared to like the game.
This game retained much of the humor and irony of the book. It manages through language. It always seemed to have a witty comeback, no matter what I typed in. If I typed in, "jump," it would respond, "Wasn't that fun?" Or if I made a juvenile comment like, "Kiss Ford," I would receive a [humorous] lecture about just what kind of game I was playing anyway. The bottom line is that the game seemed to respond intelligently and ironically. Additionally, it was challenging. Not a matter of searching around empty rooms where nothing happened—I knew approximately what was supposed to happen, and it drove me crazy trying to make it that way. The secret to getting the babble fish in your ear is...oh—if you want to cheat, go read hints online.
Honestly, I was a bit upset that it wasn't longer. Where was the sequel? But then again, a sequel would have had to be very different from the first game—and this was so good, why risk a bad sequel.
The Bottom Line
In this game, Douglas Adams has found even another way of retelling his story—and it works. Just like the radio show, just like the books, this game is the essence of fun. But the fun in this game really picks when readers and listeners have put the other media aside. To understand the jokes, one should be familiar with one of the other media.