Hi pushpitkc,
Contrary to what you presume, RC was one of my weakest sections in the beginning, despite the fact that I consider myself to be an avid reader since my childhood.

It just somehow improved over the course of time. In the exam, I spent 5 minutes in just reading the passage, and then roughly 90 seconds for each question. I just did the OG questions twice, went through the explanations, and slowly started to get a hang of what is really expected in RC. I would say that even doing the OG thrice is not a bad idea. Apart from that, if you have sufficient time, you could read various fiction/non-fiction books, newspaper editorials, articles on Quartz, Harvard Law Review etc.
For this particular section, I did not find the
MGMAT book to be good enough, that is why I could not recommend anything for it.
Hope it helps!