The following books by Dr. John Andrew Morrow are available on the Internet Archive:
The Covenants of the Prophet Muhammad with the Christians of the World in Indonesian
Six Covenants of the Prophet Muhammad with the Christians of His Time in Armenian, Spanish, Tamil, Urdu, Arabic, French, Turkish, Azeri, Russian, Persian, Indonesian, Portuguese, Italian, and Dutch
The Words of God to the Prophet Muhammad: Forty Sacred Sayings in French and Spanish
Shi’ite Islam: Orthodoxy or Heterodoxy in English and Spanish
Islamic Insights: Writings and Review
These are not self-published books. All these books were published by reputable presses, including Kazi Publications, Ansariyan Publications, Angelico Press / Sophia Perennis, and others. They are made available here for free, in various formats and translations, to reach a broader audience.
They can all be accessed here.