Ebooks:

- https://www.smashwords.com/

- https://www.tor.com/

- https://ospreypublishing.com/

- https://www.baen.com

- https://weightlessbooks.com/

- https://www.manning.com/

- https://nostarch.com/

- https://leanpub.com/

Public Domain Ebooks:

- https://standardebooks.org/

- https://www.gutenberg.org/

Audio Books:

- https://audiobookstore.com/

Public Domain Audio Books:

- https://librivox.org/