What is "alexandreis"

Alexandreis (or Alexandreid) is a medieval Latin epic poem by Walter of Châtillon, a 12th-century French writer and theologian. A version of the Alexander romance, it gives an account of the life of Alexander the Great, based on Quintus Curtius Rufus' Historia Alexandri Magni. The poem was popular and influential in Walter's own times, even being translated into Icelandic prose as the Alexanderssaga; Matthew of Vendôme and Alan of Lille borrowed from it and Henry of Settimello imitated it, but it is now seldom read. One line is sometimes quoted:

Incidit in Scyllam qui vult vitare Charybdim (Wanting to avoid Charybdis, he runs into Scylla.)