Unless you have a good reason for your file version to be different than the version of the assembly inside, I think it is a better idea to provide the AssemblyVersion alone. If you do not specify an AssemblyFileVersion, it will automatically get the same value, so you can see your assembly's version directly in the file's properties.
The advantage is that you can use a wildcard and allow the version to be automatically incremented, so that every time you compile the library you get a different build and/or revision number. As far as I can tell, this trick does not work with AssemblyFileVersion, so you have to increment it by hand.
Of course, all this only applies if you're writing .NET code. Are you by any chance talking about a project using unmanaged code?