The Heroes is another excellent addition to Abercrombie's First Law books. It's a standalone novel, but I recommend you read his previous four firstly because some character background is assumed. It is just as gritty as the previous books, but the geographical focus is a bit tighter and there are plenty of maps to let you know how the battle is progressing.
I like Abercrombie's writing style which is violent, but with intrigue to balance it out. Like Martin, he's not afraid to kill off major characters so don't get too attached.
I highly recommend this book.