I’m interested in learning more about psychological and strategical tactics/powerplays in business and real life. Right know I’m reading Machiavelli and Sun Tzu. Are there any books that you would recommend reading after those two? I found many titles and authors but honestly I don't know where to continue.
From a historical perspective, Turgot's Reflexions are very interesting. Though they are very much oriented on commerce and not so much military strategy, it provides a very interesting look into the issues at play when considering ruling a nation like France in the 18th century.
I'm sure there are many other books that could be recommended, this one is nice if you have an interest in the history of economic thought.
I'd also recommend looking at Vegetius's De Re Militari which was written in the fourth-century and proved to be the most enduringly popular and influential military treatises of the Middle Ages. An eighteenth-century translation can be found online but Penguin has republished a translation from 1940. The impact of Vegetius's work was the subject of a recent study by Christopher Allmand (The De Re Militari of Vegetius: The Reception, Transmission and the Legacy of a Roman Text in the Middle Ages, Cambridge, 2011).
Other key medieval texts include, Ramon Llull's The Book of the Order of Chivalry, Sir Geoffroi de Charny's The Book of Chivalry, and Christine de Pizan's The Book of Deeds of Arms and of Chivalry. All were influenced heavily by Vegetius and also by one another (chronologically, Llull was the earliest in the thirteenth-century, Charny next in the fourteenth-, and Pizan last during the fifteenth-century). Machiavelli also references the text in his own Art of War (1521).