This is my personal top favorite system of all time. It is very easy to learn, very easy to explain, without being rules-lite. It allows you to use pretty much any setting you can come up with, thanks to its own mechanics and how it handles all the systems. The combat is extremely fun, and very easy to make balanced encounters. I love how flexible and customizable the magic system is. Probably my favorite of any RPG. It has a lot of optional mechanics to customize the game to your own needs, and it's very easy to come up with new mechanics to further increase customization. And if you prefer working with a already stabilished setting, there are lots of great settings officially supported, like Deadlands, Pathfinder and RIFTS.

You get pretty much everything you might need for any setting with just this single book. I could go on and on telling everything in detail, because honestly, this system doesn't get the fame and recognition it deserve. It's a masterpiece.