I was not a very talented reader and have been struggling but I found correlation between my ability to understand the content of this book and my ability to read RC passage with accuracy.
It is called Cleopatra: A life by Stacy Schiff.
I did not major in History so understanding the flow of this book was a challenge but and also this book is written in a manner that required identifying tons of referential nouns and also drawing out inferences.
I recommend this book for those who did not major in English or History and are struggling with understanding complex passages. Just read during your break or before going to bed!