Christopher Matthew, A Storm of Spears: Understanding the Greek Hoplite at War. The most important conclusion from this is how the Greeks wielded their spears. Despite all the pictures, they did not hold them over their heads with a back-handed grip. Instead, they held them with the butt of the spear tucked under their armpits. This allowed for much greater reach and strength. Lots of good experiments with re-enactors.
Christopher Matthew, An Invincible Beast: Understanding the Hellenistic Pike Phalanx in Action. This is the sequel to A Storm of Spears. The sarissa (pike) wielded by the Hellenistic phalangite was much longer than the spear of of the classical hoplite, and hence had to be held with both hands. The phalangite was still able to hold a shield on his left forearm, and so wielded the sarissa underhanded. This quite different from the shoulder level grip of pikemen of the renaissance and early modern western Europe, which I practised in my re-enactment days with Clann Tartan. It is quite impractical to hold any kind of shield when holding the pike that way.
Again, Matthew did a lot of experiments with re-enactors while working on this book.
Timothy Snyder, Black Earth: The Holocaust as History and Warning. By the author of Bloodlands: Europe Between Hitler and Stalin, which I wrote about in Where 14 Million People Died. One the major themes is that of statelessness. The death camps were not located in Germany, but in occupied Polish territory. They were beyond the reach of German law, and with the complete destruction of the Polish state, also Polish law. In some parts of Nazi-occupied Europe, notably Denmark, the pre-war state authority survived in a limited form, and was able to provide some protection to Jewish citizens.
Snyder gives a chilling picture of the Nazi mindset. From this a motivation for Operation Barbarossa comes out: Hitler had to attack Russia to find more Jews to kill.
Sabine Hossenfelder, Lost in Math: How Beauty Leads Physics Astray. The standard model of elementary particle physics was essentially completed in the 1970’s. It explains very well everything in its domain and predicted the existence of various additional elementary particles which have since been experimentally discovered, notably the Higgs boson in 2012. However, there some things it does not explain, notably gravity. So theoretical physicists have wanted to be beyond the standard model, to come up with a “theory of everything” that would include the standard model, gravitation and other loose ends. The problem is that there is no experimental data to suggest a direction for this: The standard model explains everything that can be seen in particle accelerator experiments and Einstein’s General Theory of Relativity, which is outside of the standard model, can explain any gravitational observations. So in the absence of data, what do theorists do? They look to considerations of “naturalness” and “beauty” to come up with new theories. For the past 40+ years none of these theories, e.g. superstrings, has made a prediction that has been verified by experiments. Hossenfelder argues that this is futile (beauty is in the eyes of the beholder) and theoretical elementary particle physics has gone nowhere all this time, from not long after I dropped out of grad school in physics.
FWIW, other branches of theoretical physics, e.g. condensed matter, astrophysics, statistical mechanics, and chaos are doing just fine. Even classical mechanics has had something of a renaissance with new problems (the motion of artificial satellites) and new tools (computers). However the issues of elementary particle physics may be resolved, they will not affect the results of these other fields. For the “real world” any possible elementary particle theory must resolve to what is understood and has been verified by countless experiments.