There are many books available in the market but it is advisable to follow only standard books which can help you to build all your concepts better and which are easy to understand so few books which are considered to be decent for BHU UET BA course are mentioned below -

GK OF ARIHANT

Lucent’s General Knowledge

OBJECTIVE GK OF KIRAN PUBLICATION

Apart from this, you can practice previous year papers as these would be the best source for the preparation.

Good Luck!!!