The Iron Tower Omnibus consists of the first three Mithgar books (The Dark Tide, Shadows of Doom and The Darkest Day).
I know that many people think that these three books are based upon The Lord of the Rings and they're almost right about that. If I'm not mistaken, Dennis L. McKiernan wanted to write a sequel to The Lord of the Rings, but he wasn't allowed to do so, so he "re-created" Middle-earth in The Iron Tower trilogy.
These first books aren't very good, but the later books are enjoyable and fascinating fantasy books.