Suger of Saint Denis
On What Was Done in His Administration
You have two choices:
A shorter version of the treatise translated by David Burr, with a historical introduction and an appended translation of one section from Bernard of Clairvaux's Apology, also with a historical introduction.
A translation by L. A. Harkey and David Burr of the entire treatise, also with a historical introduction. (This one is a pdf file,)