The Book of Iron Might purports to do for fighters and martial characters what the Books of Eldritch Magic did for spellcasters, and it is more than up to the task. Actually I almost like it a bit better because of what it tries to do! Books of More Magical Stuff are pretty easy to find (though of course most are not up to Malhavoc's high standards), but a whole book of new stuff for fighting characters? That's much rarer.
The Book of Iron Might has many things to recommend it. It is very well organized. It has many new options for campaign and character design, including "maneuvers", to give fighters more things to do in combat. Heck, it even has a new character race that is quite similar to and predates Eberron's warforged and other "artificial" player character races!
Mike Mearls knows what he is doing with D20 and it shows through in this excellent work. As always, Malhavoc produces some of the best PDFs in the industry, though this one does not contain any extra hyperlinks or other electronic enhancements.