just dl the demo and walk around the town, talk to npc at least...
hell, i bought the battle chest (one with d1) recently just to get the manuals and diablo 1 cd even though i already have d2 (lost the manual and box tho )
Lol I remember watching my Dad playing and completing that game. I played it last year and finished it as a warrior, and I think that for all the background information the game has you should play it. Though you probably already know the story line of the original game (and if you don't you should at least read that. Theres still nothing like playing and living it yourself, trust me, you will have a better understanding of the events before D2 (and Wirt, knowing just how much of a penny-scamming-bastard he was is important), and the game is still fun.
Also, as I played D1 before D2, when I walked into Tristram I immediately went around and tried to figure out what charred burnt out wreckages equalled the buildings I remember, like Ogdens tavern.
hell, i bought the battle chest (one with d1) recently just to get the manuals and diablo 1 cd even though i already have d2 (lost the manual and box tho )
download the demo, sh!t ur pants, rinse/repeat.
http://ftp.blizzard.com/pub/demos/diablosw.exe
true. atmosphere blows d2 out of the water too.