You'd be surprised. Most of what we know about Alexander comes from flattering poets or from historians a few centuries later. We know a lot about the myth of Alexander.
Ahem. Did my Thesis on unravelling the sources on Alexander - at least on the accounts of his climactic battle with the Persians at Gaugamela. This is one of the few battles in all history before the modern literate era for which we have more than one eye-witness, even though the eye-witness accounts are filtered through several literary accounts from 2 - 3 centuries later.
First, Arrian says he used Ptolemy Soter's memoirs (which, if an original copy of them ever shows up in some pile of papyrus, will cause massive heart failures among ancient historians everywhere - it would be the greatest Classical Source find since the Dead Sea Scrolls: a personal memoir from one of Alexander's contemporaries who was also a genuine King/Pharaoh of Egypt)).
Then, both Curtius and Diodorus Sicilus give an entirely different account of the battle. BUT if you carefully analyze their accounts, and make allowances for the fact that one is writing in Greek and the other in Latin, there are over 40 instances in which their accounts are virtually identical. Furthermore, if you take all the information in those fragments (which vary from a phrase to a paragraph in length), which include a great deal of detail on the commanders and units on both wings of the Persian host, the equipping of the contingents from all over the empire, and the actions of the preliminary force sent 'up country' to try to scorch the earth in front of Alexander's advance, you will also discover that every bit is consistent with a single source who was also present at the battle: Mazayvashta, or Mazaeus, the Satrap of Babylon and commander of the Persian right wing at Gaugamela, who was also in charge of the force sent off in front of Alexander and as Satrap the man in charge of the equipping and provisioning of the entire force. He also formally surrendered Babylon to Alexander right after the battle and was promptly re-instated as Governor of Babylon under Alexander. Can you spell Political Deal in Classical Persian?
The only other things we know about Mazaeus are that he was married to a Babylonian wife and had been Satrap of the richest province of the Empire for almost 20 years at the time of Gaugamela, and that not only did he continue as governor of that province, but two of his sons became governors under Alexander and commanders of subunits of the Companion Cavalry, and that Mazaeus, extremely unusual for a Persian nobleman of his generation, died of old age.
My tentative conclusion is that he may be the most accomplished and flexible political operator in history that no one has ever heard of.