Does anyone know any books or articles I can read to learn more about Bar Kohkba?
A classic book on Bar Kochba is from famous Israeli archeologist Yigael Yadin:
but I also know of The Bar Kokhba War AD 132–135.
Talmud Yerushalmi , Taanit 4:5 (24a) and Midrash Rabba (Lamentations Rabba 2:5).
A link that I found https://www.researchgate.net/profile/Joseph_Geiger/publication/310512261_The_Bar-Kokhba_revolt_The_Greek_point_of_view/links/5c0fc0fba6fdcc494fec0241/The-Bar-Kokhba-revolt-The-Greek-point-of-view.pdf?origin=publication_detail.