VIVEK SINGH BOOK OR MRUNAL SIR NOTES

For mains syllabus, Vivek sir is best. But for Pre you can follow Mrunal sir. Mrunal sir's coverage is much more wider for Pre than Vivek sir. For ex Pillar 6 exhaustively complete many schemes of social sectors etc. 

For topics  like - Exchange rate  + more conceptual understanding of GDP topic + Understanding of investment etc  follow Vivek sir even for Pre.