Added a very good and complete book for Java and added iOS book
Update free-programming-books.md

Fixed typo.
create separate md file for interactive materials
Merge pull request #582 from jwworth/master

Some alphabetizing and typos
Added "A Guide to Python's Magic Methods"

I don't know whether this strictly meets your criteria of a "book". I'll let you decide.
16000 star in 3 month
Merge pull request #583 from sugarjig/patch-1

Added "A Guide to Python's Magic Methods"
Added "The Neophyte's Guide to Scala"
Alphabetized Scala section
make sure to keep only the fully interactive tutorials
add the new -en md file with interactive tutorials removed
Fixed Scala alphabetizing
add cleaned up -interactive-tutorials-en
Added "Play Framework Recipes"
Merge pull request #584 from alexanderfefelov/master

Scala section: a few changes
Merge pull request #577 from Mouseion/patch-interactive

Create separate md file for interactive materials
Add Hello Backbone resource

Its not strictly a book but its super helpfull for the novice
Merge pull request #585 from TechplexEngineer/patch-1

Add Hello Backbone resource
How to deal with Passwords
added Learn Git Branching Tutorial