"Dallas" was a very popular television show back in those days. Arguably, the show can claim to have generated one of the hugest (and very controversial) cliff-hangers for a weekly show in television history. Even those who never watched the show were made keenly aware of the "Who shot J.R.?" frenzy. Commercialization of television shows was not new, and there were plenty of people sporting t-shirts, buttons, and of course, bubble gum cards. My C64 friends and I never watched the show so we were never caught up in the hype, and especially cautious that familiarity with the characters of the show wouldn't be required in order to have a satisfying gaming experience.
I cannot even recall a single element of the game requiring any knowledge of the show at all.
We didn't have a lot of money as kids, and we were always as sceptical as could be before plunking down the 40 bucks or so that a new game would cost (be it cartridge, tape, or disk). We would ask detailed questions to the vendor, read whatever magazine reviews we could find (there was no internet back then), and scrutinize the box in every detail. One thing that hasn't changed since those days is the glory of being the first to discover the next great game. If I remember correctly, we picked up Dallas Quest at a computer show and we were immediately satisfied
that we had the hottest new adventure game. According to the wiki article, the game was later published for the Apple IIe, the Atari 400 and 800, and the TRS-80, so I guess we weren't the only ones who thought it was a good game.
I remember Dallas Quest keeping us entertained for hours and hours. It is the classic style adventure game with text-based commands like "Look bugle", "Open envelope", "Go South", "Inventory", etc. This type of adventure game was typically played from a command line interface with no graphic elements whatsoever. With Dallas Quest, for the first time (as I recall), we did not have to play "in the dark". This adventure game had the added benefit of visual indicators (e.g. possible courses of direction and what things are in your vicinity). The programmers took full advantage of the rich graphics and sound potential that the C64 provided and elevated the classic text-based adventure experience to a new level. If you like this style of adventure game, you will enjoy Dallas Quest.