Bruce Waltke’s nearly 500-page commentary on Micah (Eerdmans, 2007) is the best treatment of Micah I know of. It might even be the best commentary on any prophet, and ranks right up there with R.T. France’s Mark commentary. Waltke’s Micah, however, is even more technical and examines just about every textual issue you could imagine. It was indispensable to me when I wrote a seminary exegesis paper on that blessed prophet. I don’t preach Micah without consulting it.
Accordance Bible Software has just released the volume, and even though I own the print edition, I made sure to get it into my Accordance library a.s.a.p. Check it out here (Accordance) and here (publisher’s page). The price is far lower than the value of the book.