Arrian 
History of the Wars and Conquests of Alexander the Great [EPUB ebook] 

According to Wikipedia: ’Arrian of Nicomedia (c. AD c. 86 – c. 160) was a Greek historian, public servant, military commander and philosopher of the Roman period. The Anabasis of Alexander is perhaps his best-known work, and is generally considered one of the best sources on the campaigns of Alexander the Great. Its title and style are designed to evoke the Anabasis by Xenophon, for which reason Arrian became known by the surname Xenophon after the older author. Arrian’s other works include Discourses of Epictetus and Indica.’