Why should preachers, particularly lectionary preachers, read Luther? Of course there are many reasons, one of them being to study and learn from the freshness of his insights as he preaches the same texts year after year:
"Luther's sermons followed the course prescribed by the Christian year and the lessons assigned by long usage to each Sunday. In this area he did not innovate. Because he commonly spoke at the nine o'clock service, his sermons are mostly on the Gospels rather than upon his favorite Pauline epistles...Year after year Luther preached on the same passages and on the same great events: Advent, Christmas, Epiphany, Lent, Easter, Pentecost. If one now reads through his sermons of thirty years on a single theme, one is amazed at the freshness with which each year he illumined some new aspect. When one has the feeling that there is nothing startling this time, then comes a flash. He is narrating the betrayal of Jesus. Judas returns the thirty pieces of silver with the words, "I have betrayed innocent blood," and the priest answers, "What is that to us?" Luther comments that there is no loneliness like the loneliness of a traitor since even his confederates give him no sympathy. The sermons cover every theme from the sublimity of God to the greed of a sow."
From Roland Bainton, Here I Stand: A Life of Martin Luther (Abingdon, 1955), still one of the best popular biographies of Luther, available on-line here. English translations of some of Luther's sermons can be found here. There are also sermons available to the English reader in the American Edition of Luther's Works, which edition is presently being expanded by Concordia Publishing House with the inclusion of three further volumes of sermons.
Luther preached an estimated 7000 sermons in 36 years of preaching (!), of which about 2300 survive in written form. He followed the traditional one year lectionary, whereas most preachers today have the luxury of a three year lectionary. One must remember too that most of Luther's sermons were delivered to the same town congregation, whereas preachers these days expect several calls in their time of ministry. Nevertheless, most contemporary preachers will have struggled with the need to maintain freshness (which is different from novelty!). In that endeavour Luther can be a valuable teacher.
The pic is of the pulpit in the town church in Wittenberg; it's a pity the drab, ill-conceived parament detracts from an otherwise impressive scene.