I agree, Shampoo Planet is also the far better book, funny and really accomplished (rather than just a collection of ideas like Gen x: Tales was), really one of Coupland's best, along with Hey! Nostradamus, and All Families Are Psychotic.
From a European perspective, i think a big reason why Gen X took us by storm was two-fold:
Up until that point we (my generation) didn't think we were anything. Now suddenly there was a label for us shadowy misfits who didn't fit neatly into what was already trite and worn-out stereotypes: Hippies, punks, skinheads, rockers, yuppies... Also, the 'x' - sufficiently abstract - helped soften the blow of being labelled at all for a generation vehemently opposed to being labelled.
Secondly, and i think this point was obscured for the longest time (much like a tiny orbit moon is overshadowed by a planet) that was all the furore of the gen x label and all the gorgeous new concepts like McJobs etc that came along with it):
The real insightful social commentary on what was going on on a much deeper, more impactful and so far enduring level was that we (Europeans) were, and are, now default americans.
Or McAmericans, if you will.