_{Use an e-Book manager like Calibre to manage and convert your e-Books, it provides a good interface.}

General E-Books

• Anna’s Archive - Search Engine that indexes a few big libraries including libgen and Z-Lib.
• Z-Library - The Library is also accessible through Tor and I2P, Requires Sign-up.
• Library Genesis (.fun) & .rs | .is | .st - The .fun domain is currently being run by the original owner of libgen whereas the others are independent.
• Mobilism (.me) | .org - Forum, Requires Sign-up.
• MYWAREZ.ORG - Forum, Requires Sign-up.
• The-eye - Many e-Books and calibre libraries.
• eBook Hunter
• Ebookee
• OceanofPDF
• PDF Drive
• My Anonamouse - Has a lot of content, including niche e-Books and audiobooks. Friendly community and mods. An easy to get into Private Tracker, Requires Sign-up.
  Be sure to check our PT page for more info regarding Private Trackers.
• Project Gutenberg - Legally free e-Books.  
   

Audio Books

• Mobilism (.me) | .org - Forum, Requires Sign-up.
• Galaxy Audiobooks
• MYWAREZ.ORG - Audiobooks section of a Forum, Requires Sign-up.
• LibriVox - Legally free audiobooks  
   

Scientific Journals/Technical Manuals

• Sci-Hub (.se) | .st | .ru
          Sci-Hub X Now! - Opens the Sci-Hub page for the article you want to read.
          Zotero Scihub - Addon for Zotero and Juris-M to automatically download PDFs from Sci-Hub.
• SciMag - Scientific Articles section of LibGen.
• Free Full PDF
• Freetechbooks
• r/Scholar - If you can't find an article anywhere, you can request it in this subreddit.  
   

Other

• Rave Book Search Engine - A search engine that indexes many Comic, e-Book and Audiobook sites.
• CALISHOT - A search engine indexing many open Calibre servers, also has a Non English Books Section.
  If the links stop working check here for updated ones.
• Archive.org & Open Library - Has a lot of niche historical content.
• Trantor - Darkweb e-Book resource.
• Flibusta - Russian e-Book site.  
   

Tools

• DeDRM - Tools to be used with Calibre to remove the DRM of e-Books from various retailers.
• Bypass Paywalls Clean for Chrome & Firefox - Bypass News Article paywalls.
  Backup site for updated extension files.
• Unpaywall Browser Extension: Chromium & Firefox - When you view a research article, Unpaywall automatically looks for a copy in its index. If it finds one, click the green tab to read the article.
• 12ft Ladder - Removes clutter from News Articles.
• Open Access Button - Search engine for research articles.
          Browser Extension Chromium & Firefox
• Libgen Desktop - Windows application for browsing a local copy of the LibGen catalog.  
   

IRC

• IRChighway.net/eBooks - Use this guide or their official FAQ to learn how to use the commands.