Project Gutenberg:
Project Gutenberg History Books offers a large collection of classic historical texts available for free download in various formats.
Internet Archive:
Internet Archive History Collection provides access to millions of free books, including many on historical subjects.
Google Books:
Google Books has a selection of free e-books and previews related to history. Simply search for historical topics and filter results to show free e-books.
Open Library:
Open Library History Books offers a vast collection of free history books that you can read online or download.
ManyBooks:
ManyBooks History provides a variety of free e-books, including those on historical subjects.
BookBoon:
BookBoon History Books offers free e-books on history written by professors and industry experts.
PDF Drive:
PDF Drive History Books has a large collection of free PDF e-books on historical topics.
These resources offer a broad selection of historical e-books, from ancient history to modern times, all available for free.