Question: Hello,

I'd like to hear your opinion for ergodic theory books which would suit a beginner (with background in measure theory, real analysis and topological groups). I am looking for something well structured, well motivated, and perhaps with application to other fields.

any such book exists?

I tried a book by nadkarni, and could not read through it, seemed to concise to me, and tried the book by Petersen which I felt was accessible but didn't follow a clear path, jumping from subject to subject with lots of different object or properties.

What are your recommendations on the subject?

Answer: 
I really like (and recommend) Billingsley's *Ergodic Theory and Information*. It is a well-written book with very clear explanations. For example, his treatment of entropy tops those in both Walter's *An Introduction to Ergodic Theory* and Petersen's *Ergodic Theory*, both of which are also good books though.
I recommend Foundations of Ergodic Theory by Marcelo Viana and Oliviera <https://books.google.it/books/about/Foundations_of_Ergodic_Theory.html?id=vlRyCwAAQBAJ&printsec=frontcover&source=kp_read_button&redir_esc=y#v=onepage&q&f=false>
This book has almost everything explained.