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 think another good choice is the book "Ergodic Theory: With a View Towards Number Theory" by Manfred Einsiedler and Thomas Ward,Graduate Texts in Mathematics 259.Besides basic concepts of ergodic theory,the book also discusses the connection between ergodic theory and number theory,which is a hot topic recently.And a forthcoming second volume will discuss about entropy,drafts of the book can be found on the homepage of Thomas Ward (<https://tbward0.wixsite.com/books>).
Personally, I like Mañe's book Teoría Ergódica. I do think it's a classical book full of exercises. On the other hand the book has loads of mistakes, which makes it interesting to read, you realise that you are understanding everything when you spot the mistakes. As far as I know, both versions (English and Portuguese) are sold out.