Best book for understanding Unity 2D

What’s the best book for understanding Unity 2D? There must be some guide which teaches the  principles/ characteristics/ dynamics  of Unity, and not just the basics like “how to print HELLO WORLD” or the steps to creating a game. A book that takes beginners to a more efficient path of learning and not just a prolonged trial and error process. For example I wish to understand how layers and cameras work, and the videos which I find on youtube or even the books I can find only show steps to doing something, but omit to explain why those steps are taken. Please don’t direct me to the Unity manuals. They tend to omit something here and there. 

Hi I recently used Learn Unity for 2D Game Development By Alan Thorn, not a very cheap option but useful enough. In general, I recommend that you read reviews on the Internet for books and make a choice yourself, it will be many times more effective, and in general such book reviews always help, but I recommend you / get acquainted with examples of cool analyzes of the novel “In Cold Blood” by Truman Capote, go on and read these articles for general development, and also pick up analysis and analysis of other thematic books that may be interesting to you, it is really interesting, useful and easy, good luck to you!