So I have been reading this series for a while now. I have lapsed and only returned to it with the first The Books of Glittering Stone - Bleak Seasons.
This is a very good series of books. It is essentially about a mercenary company known of as The Black Company and their experiences as told through the Annalist Croaker (at first). It is very well paced. The action in some parts is very short and simply told, but very satisfying. Glen Cook (the author) manages to paint a very vibrant picture in some of these action scenes without being terribly verbose.
It starts out with The Book of the North series which sees The Company being employed by the powerful sorceress simply known as The Lady and their interactions with The Rebel and The Ten Who Were Taken (other power mages)
What I feel makes this series very interesting is that The Black Company is never really a heroic group. Sure they do some heroic and good things, but most all of their actions are done in order to keep The Company alive. They aren't out to save the world. They are a mercenary group that does at times do brutal and terrible things, but they largely set out to do the lesser evil of things when it comes down to it.
Another thing I like is way magic is handled. The Company has a few spell casters of it's own and in the setting at large wizards and the like are few and far between. The Companies wizards are not all terribly powerful. Magic is powerful, but only a few actually can sling spells about such as The Lady and The Ten Who Were Taken. Also sorcerers are not push overs when it comes to durability. Just read it, it is cool and not typical wizard's firing off fireballs, though there is some of that.
This is a great fantasy series that I feel you should check it out if you are a fan of fantasy or dark fantasy.
Start with the novel simply titled The Black Company