Which are the best books for Preparing PCS Exam?

You have not mentioned the subject for which you want to know the books. However for General Study Exam you can refer NCERT books from class 6th to 12th. Besides you can go through India Today, Pratiyogita Kiran, One Local and National News paper for the current affair section of the GS paper of PCS Exam. Some of the other good books for PCS Exam are:

1. Indian politics by Lakshmikanth
2. Ancient India by D.D.Kausambi’s Historical Outline
3. Medieval India By J.L.Mehta
4. General Studies Manual 2011
5. Gandhi & Subhash By B.L.Growers
6. R.P.Sharma G.K. & G.S
7. A.L. Basham's Buddhism & Jainism
8. Public Administration by Urmila sharma and S.K. sharma
9. Civil Services Interview Success Profile & Personality Development by Dr.K.K. Sharma
   
10. Civil Services Success Planner by Dr.K.K. Sharma
11. The Punjab civil services rules: Volume 1, Part 1 and 2, Volume 2 by Punjab (India). Dept. of Finance, Punjab (India).