I use the following sites to get free e-books on faith based topics:
Project Gutenberg http://www.gutenberg.org/wiki/Main_Page/
Way of Life Literature https://www.wayoflife.org/
Wholesome Words https://www.wholesomewords.org/index.html
And of course... http://www.preservedwords.com/
I also use "PDF Studio Viewer" (https://www.qoppa.com/pdfstudioviewer/) for viewing PDF files, it has some nice features for us Linux users. They no longer make Acrobat Reader for Linux, so this is a nice alternative.
I hope that help some of you.
.\\itch - Prv. 3:5-6 Trust in the LORD with all thine heart; and lean not unto thine own understanding. In all thy ways acknowledge him, and he shall direct thy paths.