The NCERTs are considered to best books for beginners to start their preparation for UPSC exam. Some of the best NCERT books for UPSC examination are –
India and contemporary world (Class 9th),
Understanding Economic development (Class 10th),
An introduction to Indian Art (Class 11th)
Indian constitution at work (Class 11th)
To check detailed booklist for NCERTS, you can download the NCERT book list for UPSC.