Here are some reliable sites that make available older books that have been scanned and some descriptions to help compare them. There could be more than one copy of a title within a site (as well as across sites), so sift through results and virtually flip through some pages!
- https://books.google.com/ - Well known to be a comprehensive index of full-text books through the Google Book Project
- Internet Archive - San-Francisco based nonprofit digital library (Also see Archive-It from the same organization; contains digital special collections of cultural heritage.)
- Early English Books Online - An open access project containing many Puritan works.
- HathiTrust Digital Library - Seeks to digitally preserve and make available public domain material from various other sites
- Project Gutenberg - Thousands of freely available ebooks, for download or to read online
- DOAB - Directory of Open Access Books provides a portal for academic publishers to make available peer-reviewed books that have been published in open access.
- FirstLove Publications - FirstLove Mission provides Biblically sound books, booklets, tracts on doctrinal, evangelistic, apologetic, and devotional subjects.
- Third Mill - This page will lead you to a variety of electronic resources, including e-books, available through Third Millennium Ministries.
- Frame-Poythress.org - This site contains pieces (many excerpted from published books) written by two well known Reformed theologians and authors, John Frame and Vern Poythress.