Yes, that was indeed a classic story (for the uninitiated, the story is "Light of Other Days" by Bob Shaw). It's one of my favourites. But when I read it, a few minor problems with slow glass occurred to me.
One is refractive index. Since RI of a substance is the ratio of the speed of light in a vacuum to the speed of light through the substance, the RI of a sheet of slow glass 10 years "thick" and say 1cm physical thickness, would have to be around the 9.47 billion billion mark, which would lead to some pretty way-out optical distortion if you looked at it from any angle other than head-on.... trippy!
Even assuming they got around the RI problem, there's the issue of privacy. See - you buy this stuff from a hillside in Scotland with a lovely view of the glens, and hang it up in your lounge. It lasts for 10 years, after which you are briefly treated to the visuals of the journey from Scotland to your place, and finally a lovely view of your lounge-room wall as it was a decade ago. So you take it back up to Scotland and swap it over for a new piece. Very good, no? Well, considering the sales guy was using it to watch the past of his dead wife and child, there's just one small problem; the OTHER side of the sheet of slow glass is now radiating out the last 10 years' worth of all the goings on in your lounge-room, dumped nicely out on a publicly-viewable hillside in Scotland for the next decade for all comers to see...
And they thought Google Street View was bad! ;)