Unity has been giving away lots of FREE ebook content that can be hidden if you don’t know where or what to look for.
some of the best Unity Books are;
1: Unity From Zero to Proficiency (Foundations)
2: Developing 2D Games with Unity
3: Unity UI Cookbook
4: Learning C# from Developing Games with Unity 5.x
5: Unity 5.x By Example
You can master Unity in a week in only 7 easy steps:
1.) Start watching the unity tutorials and try working with the examples they provide.
2.) Implement their ideas into your own game and build on top of them.
3.) In about a year or two you should be very decent at making any sort of Unity game (previous c# knowledge helps immensely)
4.) Spend the next 40 years studying theoretical physics
5.) Us the knowledge to build a time machine
6.) Travel back to 2016, a week from now. Kill and replace yourself.
7.) You have now mastered unity in under a week.