https://freembook.com/
https://www.jiumodiary.com/
https://www.soushu.vip/
http://www.banshujiang.cn/
(程序员书籍很多)
https://www.sanqiu.mobi/
(页面美观,可适用kindle)
https://ebook2.lorefree.com/
https://manybooks.net/
(英文电子书)
http://www.tuishuge.com/
(kindle适用)