Is there any good book about game development? Maybe a book about Unity or something? I know C#, some C and some Java. Should I first learn any other language?
Are you looking for a technical book, to learn how to code and create games on unity?
Or for a book of someone working in the video game industry, and sharing his knowledge and experience through anecdotes?
I cannot directly answer to your question, as I never searched for a book covering Unity, but I can recommand the official documentation, their community, the programming sub-forum of mpgh, and especially the tutorials on youtube which are very rich.
The issue with writing a book or making a tutorial for Unity, is that this software is really complex, and there are several ways to achieve what you want, through programming or through the built-in tools, and the possibilities are infinite. The best way to learn is by trying, searching online for answers when you're stuck, and by creating a very simple game as a beginning.
Creating a game takes a lot of time, requires a lot of different skillsets (being good as a game designer, 2D or 3D graphist, 2D or 3D animator, musician, programmer, scriptwriter...). As a beginner, you can't work miracles, even with the best tools ever.