>as well as info on how armor evolved, like what technological advances were made to go from maille to plate and stuff like that.
Let's see, a good starting point is IMO Edge&Paddock, "Arms and Armor of the Medieval Knight".
Then for a more specific look into the stylistic changes in plate armour you get Oakeshott's "European Weapons and Armour".
For the metallurgical side of things, some bits about the craft, and an analytical look at performance get William's "The Knight and the Blast Furnace".
Know what? Just get Williams no matter what. You want it. And "The Sword and the Crucible". Those two books need to be read.
Hall's "Weapons and Warfare in Renaissance Europe" provides context to some of it.
For a short answer we probably see a combination of metallurgy giving you larger plates to work with and more powerful weapons pushing providing the impetus for changes in armour, which occasionally goes a bit too far (transitional plate, great helm) and gets dialled back a bit (transitional plate to full plate by the removal of a lot of mail). Then we get thicker plates here and there as people compromise between bulletproof and lightweight, eventually deciding that it isn't really worth the bother any more.
In somewhat related news, my copy of Capwell's "Armour of the English Knight 1400-1450" finally showed up yesterday. For some reason they thought that this was the proper way to ship it (with your standard carton book box swimming around in there).
