1977 was the year the sci-fi film Star Wars came out. Technology fan Douglas Adams, would surely had seen it. His book reminds the film with all the galactic travel, spaceships etc.
Also the idea of a guide reminds us of very famous 19th century travel guidebooks by Thomas Cook or George Bradshaw. These two were extremely popular guidebooks used by travellers of 1800s. Douglas Adams himself got the idea for his book lying down watching the stars with a guidebook in his hand.
THE HITCHHIKER'S GUIDE TO THE GALAXY 