All of these books are made available free of charge in the public domain. They have been released under the GNU Free Documentation License, the terms of which are available here:
GNU Free Documentation Licence.
Please note that these titles are available copyright free in the USA, other countries laws may vary and you should find out before downloading. Most of these books are either the open source "epub" versions that can be read in most ebook readers or the Kindle "mobi" version.
At present I have very little time to read, review or add new titles. If you can't find what you want here, I recommend either Project Gutenberg, Feedbooks or Manybooks, each of which have a vast amount of books available in the public domain.
Everyone is a genius, but if you judge a fish on ability to climb a tree it will live its life believing it is stupid
SFBook is entirely funded by Ant including hosting, development and any other costs.
If you enjoy the site please consider a small donation towards the cost of the upkeep and development of SFBook.