Hi, I recently started watching Game of Thrones, and through that fell into a phase of wanting to learn phycology, philosophy, and actual tactics of Medieval War. I was wondering what some not crazy difficult book recommendations "I'm a Highschooler" would be on Medieval War Strategy that is a good fun read "or audiobook preferably", and is not so much of just a historical standpoint on the topic but more so of, why they did this, the phycology behind it, the philosophy behind it, and everything in between. Thanks!
I recommend the following five works as the rock on which to build your understanding of medieval warfare. They are not all easy to read, Warfare in Medieval Europe 400-1453 is particularly dense, but they will all add to your understanding of the subject. In general, the newer works supersede the older works when it comes to facts, so when there is a contradiction, then the newer work is usually the correct one. I don't believe that this is always the case, but this usually comes down to differences of opinion, not fact. If you only read one of the books, then Medieval Warfare will provide the best overview, though I disagree entirely with Timothy Reuter's section of the book.
History of the Art of War, Volumes 1-3, by Hans Delbrück, for insight into infantry and cavalry dynamics, how to use topography and logistics to examine the veracity of battle accounts and various useful miscellaneous pieces of information and primary source quotations.
The Art of Warfare in Western Europe During the Middle Ages, by J.F. Verbruggen for detail on the psychology of medieval warriors.
War in the Middle Ages, by Philippe Contamine for some of the societal aspects of warfare.
Medieval Warfare, edited by Maurice Keen for early medieval Scandinavian warfare, warfare in the High and Late Middle Ages, equipment, sieges, naval warfare, use of mercenaries and the effects of warfare on civilians.
Warfare in Medieval Europe 400-1453, by Bernard and David Bachrach for how to use primary sources, logistics, finance and Carolingian and Ottonian warfare.
If you want a look at the mind of the medieval warrior, the primary sources are excellent for this. Jean de Joinville's The Life of Saint Louis and Geoffrey of Villehardouin's On the Conquest of Constantinople are two valuable looks into the mind of a medieval knight.
For a look at the kinds of questions and moral dilemmas medieval warriors had, then Christine de Pizan's The Book of Deeds of Arms and Chivalry has a large section devoted to both the questions and answers of this nature, as well as being an important source on early 15th century warfare.
Edit: I've just now been reading Bloodied Banners: Martial Display on the Medieval Battlefield, by Robert W Jones, and I think this would also suit your needs, as it delves quite deeply into the psychology surrounding arms and armour and their effect on opponents.
I can point you in the direction of some quick reads that might get you into the mindset!
Vegitius' works would have been pretty central reading for a lot of Medieval Nobles readings. Vegetius was a Roman living in the late Roman Empire (4th century).
Machiavelli' "The Prince" might help get you into the mindset of a Tywin Lannister or a Stannis Baratheon type character.
Both should be either really cheap or maybe even free on an eBook. If you want something more in depth, then you can always go to a public library and look some up!