I'm finishing up "The Steel Bonnets" by George MacDonald Fraser (one of the finest English language writers in my opinion) and it's got me curious to learn more about the border reivers. Fraser has a very short section on the reivers' arms and armor, basically stating that they preferred lightweight leather sewn with plates, tall leather boots and light mail to the more common breast-and-back of the time. I'd like to know more about the gear of the period, and would appreciate any book recommendations on the subject.

Try the Osprey book series. I know they have at least one title on the Border Reivers and there may be another.

The Steel Bonnets is a very good book but tends to be a little repetitious. It is also difficult to keep all those "Watts" and "Willies" separated. But, a worthwhile read on the subject.

There is a book from Alistair Moffat called the "The Reivers: a story of the Border Reivers" so far not bad but haven't read as much as I'd have liked to.