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'd recommend "Introduction to Ergodic Theory" by Nathanial A. Friedman. The book is reasonably concrete and short and treats the important "cutting and stacking" constructions in detail. This only will help you with the measurable setting and is an older book, though.