The Spirit Lens — Carol Berg

For Portier de Savin-Duplais, failed student of magic, sorcery's decline into ambiguity and cheap illusion is but a culmination of life's bitter disappointments. Reduced to tending the library at Sabria's last collegia magica, he fights off despair with scholarship. But when the King of Sabria charges him to investigate an attempted murder that has disturbing magical resonances, Portier believes his dreams of a greater destiny might at last be fulfilled...