In addition to the most straight forward box set title of all time (even 50 Chilling Classics is a bit vague in comparison), 5 Films By Dario Argento is a pretty good set, despite the lack of any of his top tier titles such as Suspiria or Deep Red. Hopefully another collection from Anchor Bay will find its way to shelves later this year (the rights to Argento's films are constantly changing hands).
But these 5 are a good way to be introduced to the master. You should start with Trauma, which is a good film to start with, as it combines the sort of strange feeling of his earlier films with the accessibility of his later work. Depending on what you like more, you should then go back and watch Tenebrae and Phenomena for more of a classic Argento approach (i.e. some of it doesn't make any goddamn sense), or go forward and watch Do You Like Hitchcock? and The Card Player, which are more standard, direct thrillers, albeit with a few classic Argento touches.
(the above links will take you to the individual reviews - don't forget there are spoilers)
All five films are good or great, there is no outright stinker in the box (of course, Argento only has one such film in his career - Phantom Of The Opera, which is ironic since his all time best film is a modernization of the story, simply titled Opera). And the price is much less than the cost of the five films bought separately, so if you don't own any, this is an easy purchase.
It's also a compact release - the metal casing only takes up as much space as a normal DVD would on your shelf, despite the fact that there are 5 discs. The discs are placed inside much like recent TV releases, with two discs on a plastic tracy, one halfway below the other. This means you have to take out the 'front' disc to reach the 'back' one, but they are quite sturdy, which is more important in the long run (if you want to know how NOT to package a DVD set, feel free to check out the horrendous HD release of Battlestar Galactica Season 1 - it's just about the worst thing I've ever seen).
Highly recommended, and please buy it, so we get another collection. Thanks!