Volume 5, the latest one, was just added today to NBM’s catalog on Comixology, get it here, and see the free preview. Volumes 1 and 4 are also available.
Comixology’s catalog of NBM graphic novels has been growing quite handsomely, check it out!
Recently added too: Stan Mack’s GN on the American Revolution. The hardcover is $15, the e-book only $9.99.
NBM Blog 