The first book in the HHGG series was The Hitchhiker's Guide to the Galaxy, and the name of the Gatehopper's Guide to Proelium was an intentional reference/homage to the series. The 'Guide' in the books is an electronic encyclopedia, which has the words DON'T PANIC printed on its cover in large, friendly letters.
The Hitchhiker's Guide books:
HHGG is not the same as [h2g2], an online community and collaborative encyclopedia based on the Hitchhiker's Guide. h2g2 was Douglas Adams's idea.
If ever you want to read something funny, read the Guide. If ever you need a book on which to write an ongoing plot summary as you read, for a class, for the love of mashed potatoes, pick ANYTHING ELSE. Somewhere I still have a notebook full of "I think they're just throwing the plot out the window. But there's a sperm whale! Hi, sperm whale!"
The text game is even worse. --Ree