The nature of questions from S & T in UPSC has changed a lot, especially since 2013. Now UPSC focusing on applied sciences rather than theoretical parts. Thus, basic science books (ncert) are maybe not sufficient for the preparation of this segment.
On the basics of trend analysis of S&T Space science, Biotechnology, Nanotechnology, Robotics, ICT are very important topics. UPSC always asked various types of questions from these topics.
So, we have to pay special attention to these topics in our S &T. we also include the latest technological developments in special classes.