What is AMD Mantle, and can I take advantage of it?

I've bought Civilization Beyond Earth in Steam, and when I start it I get the option to just start the game, or to start it using AMD Mantle.

There's no explanation of what AMD Mantle is.

I have an AMD card (I'll post the exact model later when I'm back at home - but it's pretty top spec and only a year old).

Should I just select the AMD Mantle option and will I get any benefit?

AMD Mantle is a new API by AMD that's supposed to make games run faster by giving them even lower level access to hardware than directx or opengl. However its in its early stages, and you may experience some buggyness. Anandtech seems to like it, and its benchmarks indicate its faster - though early tests seemed to be buggy

Its worth a try - there's probably no real issues with switching back to the regular renderer if you're unhappy with mantle, but when it does work, mantle is faster.

As per Wikipedia:

Mantle is a low-level rendering API targeted at 3D video games. Mantle was originally developed by AMD in cooperation with DICE starting in 2013. Mantle was designed as an alternative to Direct3D and OpenGL, primarily for use on personal computers, although suitable hardware is fully available in the Wii U, PlayStation 4 and the Xbox One.

Summary:

The main advantage of Mantle is the low CPU overhead, which improves performance in games that support it.

The main disadvantage of Mantle is the fact that it's new and games might be buggier in Mantle than in DirectX.

Additionally, since the release of the Mantle API Microsoft has revealed DirectX 12 which is supposed to provide Mantle-like performance and is also meant to be backwards compatible to DirectX 11 hardware, meaning developers may have less reason to use Mantle.