The final volume of the manga was released some time ago, but it is just now that the first english translation has been completed. You can find it here.
I first saw Shigurui as an anime. It was an intriguing piece for its pacing and of course its violence. Shigurui has a much darker and more sincere portrayal of samurai then is often displayed in many manga or anime. The author's ability to turn fights ended by a single sword stroke into a dazzling battle spanning moments lasting ages is truly incredible. While there is plenty of gore in Shigurui, easily comparable to say Gantz, it is a story full of much more cruelty. Many of the characters suffer merely by existing.
The final volume seemed very brief. It was also a very unexpected end. I felt it very poingant how both Irako and Fujisuke were defeated. All of the four main characters lost in the final fight.
If you can stand the violence, then it's worth a read. And if you enjoy Shigurui, then I'd suggest reading the novel it is based on--Suruga-jou Gozen Jiai.