EPPlus .dll Can't define in assemblies.

I'm trying to investigate EPPlus package, as I need to READ an xls doc, and so far, all the info I found is about to write xls..

But copyed the .DLL to the root of my project, and on the Add Assembly Reference, got a message that assembliy can't be loaded.

I'm using the dotnet4 version, it's a dll.

I wonder if anybody has being able before to use it?

Thanks.!!