The books depends on your interest. As , there are many books available for reference it depends on you which you want to read. Here are some books which you can refer :

Sakurai - MQM and AQM

Schwabl - AQM
Weinberg 's books on QFT

For relativistic quantum mechanics:
Greiner - RQM
M. E. Rose - Relativistic Electron Theory.

For Path Integral theory, Dirac & Feynman 's original papers.

You can refer the ebooks also or can buy them.