List of free book stuff for developerππ½
If you're looking for all programming tools around book (not just free). Check this page List of book Programming Tools

Flaviocopes ebook
Flaviocopes, popular developer blog offers 10+ free ebooks around python, linux command, react, svelete, etc.
Tag: book

Free Programming Books on Android development, C, C#, CSS, HTML5, iOS development, Java, JavaScript, PowerShell, PHP, Python, SQL Sever and more