A translation of two books on the philosophy of the Itto School of Sword Fighting. Book 1: The Twelve Rules of the Sword. Book 2: The Sword Manual of Kanamaki Jizai. The first is attributed to Ito Ittosai the legendary swordsman of the 16th century. Ittosai travelled the country and fought the head students of 33 schools, winning every time. The second is a 16th century instruction manual attributed to Ittosai's teacher Kanamaki Jizai. These books are essential for understanding the development of traditional Japanese sword arts and Kendo.
While there are a few tidbits in here that are worth knowing, like other older books on sword work, it's a little frustrating because many of the things that were taught were purposely not written down. Understandably they are hard to put into writing and were generally vocally taught to the student. This makes it hard when someone is grasping for knowledge on the subject, only to be kept from it again.
Regardless, there are some good points, not really techniques, but methods and ways of thinking. Speaking of that, I'd argue that the 12 could be reduced to fewer since many of them are basically to clear your mind, which I've read in other books too.
One thing I liked were pictures of the original scrolls, listing the rules along with their translations.