Hello Aspirant

The best books for GAPT exam are listed below:-

Pharmacological basis of Therapeutics

Basic and clinical pharmacology 14E

Basic and clinical pharmacology

Modern pharmaceutics

Physical pharmacy

GPAT: A companion

Text book of pharmacognosy(E.Walis, Treas and Evans)

Chromatography

Spectroscopy and titration

Organic chemistry

Industrial microbiology

Advanced physical chemistry  

These are the some books which you could recommend.

Thank you!