A very interesting setting-agnostic system which reminds me of the old Dream Park book by R. Talsorian Games: light on rules, heavy on support material. It somehow manages to avoid the rules bloat common in other systems while providing ample support for the most usual genres (fantasy, sci-fi, horror and superheroes) with a good sampling of advantages and disadvantages, archetypes, spells, psionic powers, superpowers and equipment, but it would be very easy to add or adapt more if needed. If you head to Elemental's Facebook page you will find unofficial conversions for Aliens and Fallout and a good number of popular Marvel/DC superheroes. The "official" adventures available also do a good job of showcasing the system's versatility.
The One Page Rules also available on Drivethrurpg contain all the information a player may need in most cases. You only need two d6 (one for the player, other for the GM) to play, but the rules support partial successes and a limited form of exploding dice called "break". The Complete Guide expands on the One Page Rules and also adds rules for chases and other special situations, all of them handled in a very simple, unobstrusive way. I think the chase rules could easily be used to play out other kinds of extended or complex conflicts with a little work, BTW.
If there is a gripe in the book for me are the whimsical names of some of the spells in the Fantasy chapter. "Caeradinn’s Elemental Discourse" or "Gideon's Fragmented Perceptions" sound nice, but I would have preferred to see a more "generic" denomination. It is really not difficult to figure out what the spells do, so it might be just me, but they simply do not feel "generic" enough for me. Other than that, if you are on the market looking for a simple but complete enough and easily expandable ruleset, you should have a look at Elemental.
There are a couple of caveats, though:
1) This is not a game for GMs new to tabletop rpgs, as it assumes you already know what tabletop roleplaying. It should work beautifully with new players, though.
2) I guess the author wanted to keep the page count down, but perhaps a few more examples and a bit more of meat on vehicle combat and use would have been nice.
On the other hand, I really like the simple, readable layout and tables (even though the illustrations were repurposed from those offered by Sine Nomine Games). There is even an index, which is a nice touch.
[Edited to add a couple of points]