The original term behind "emptiness" is a lot richer than this english word. That's why many books leave those words as is, e.g. rig-pa.
"Emptiness" of your mind means something like a thin soap bubble around you. This bubble acts as a lens, it can enlarge arbitrary things, it can create stable patterns on its surface, and all that is useful, but it blocks whatever is outside the bubble. In its natural state it would be a perfect invisible sphere, letting you see outside: this union of clarity and emptiness creates wisdom. You are still going to use this bubble as a whiteboard for your thoughts, but you'll also know how to see thru it.
The concept of emptiness applies to material world in general: the western science calls it space-time, the idea that any thing can turn into any other thing, for both are fundamentally just motions of energy that has no natural shape. Buddhism tries to teach this basic idea in different terms.
For some reason that I don't quite understand, the founders of the three religions had fragmented the truth: buddhism teaches wisdom, christianity teaches love and islam teaches action - the three aspects of the spirit. Perhaps they thought that mixing everything into one bag would be too difficult to grasp, or maybe they hope it will make the peoples collaborate to assemble the pieces.