Could you recommend any good authors or Christian books?
Martin Luther has some valuable books (e.g., “Bondage of the Will”), as does John Calvin. Although the age of these texts can make them difficult to read, they are worth the effort, as are the works of many of the Puritan authors of the same period. John Owen and Jonathan Edwards are two authors that come to mind.
Obadiah Grew’s “The Lord Our Righteousness” is a must read for every Christian, and James Buchanan has a great book called “The Doctrine of Justification”, originally published in 1867. J. Gresham Machen (early 20th century time period) has some good books, with “Christianity and Liberalism” being his most famous. Among modern authors, we recommend virtually anything written by John MacArthur, R.C. Sproul, Michael Horton, Arnold Fruchtenbaum, James Montgomery, Alistair Begg and James White.
Keep in mind that no human author is perfect in their understanding of Scripture, so each of the aforementioned authors may teach incorrectly from time to time.