Hello Rohit,

Best books for preparation of MPSC (Drug Inspector) are listed below.

Ramesh Mental Ability Test - Author: Manoj Kr. Singh

Handbook on Injectable drugs - Author: L. A. Trissel

General Knowledge Digest and General Studies - Author: S. Chand

Ophthalmic Drug Delivery System - Author: Marcel Dekker

Profiles in Drug Synthesis - Author: Gogate

Unique Quintessence of General Studies - Author: J.K. Chopra

Controlled Drug Delivery: Fundamentals and Applications - Author: Robinson, J.R. Lee

Mental Ability Test by R.P.H Editorial Board

A Global History of Narcotics

I hope this information was useful to you.

Best of Luck!!