Luther said that Christians are drawn away from the faith by curiosity (Eastern Orthodoxy and Romanism today) and satiety (an abundance of orthodox Lutheran congregations). When we had large conservative Lutheran congregation rising out of the farm communities of Middle America, we grew bored and tired of conservative Lutheran doctrine. Our itching ears wanted to hear about all the fads rolling through our culture. Now we even have a culture watchdog, who is the essence of faddism: Leonard Sweet.
Here is my list of the best things to read, then to read over and over. My library is small but choice.
Luther's Sermons, the Lenker set in 8 or 4 volumes.
Concordia Triglotta or the Tappert edition.
Chemnitz' Two Natures of Christ.
Chemnitz' Examination of the Council of Trent.
I would add these hymns:
1. Any hymn by Luther, Gerhardt, or Martin Franzman.
Many of Luther's hymns are neglected. Pastors do not select the lesser-known ones. Then people do not learn them and they remain lesser-known hymns. "Flung to the heedless winds" is a great hymn with a beautiful melody. Luther wrote that hymn, his first, after two young men were burned at the stake in 1523 for their Lutheran faith.
There are many other great Lutheran hymns. I wish Lutheran pastors and their choirs would emphasize the greatness (pure doctrine) of Lutheran hymns rather than the temporary popularity of spiritual ditties.