dear aspirant,

You can build a base for the subject by going through all the NCERT books from class 6th to class 12 th.

Other books you could refer for optionals:

• Geomorphology by Savindra Singh
• Climatology by D S Lal
• Physical Geography by Savindra Singh covers geomorphology, climatology, biogeography,oceanography and environment geography. ONE book for complete PHYSICAL GEOGRAPHY.A MUST READ.
• Models in Geography by Majid Hussain.
• Geographical Thought by Majid Hussain or R D Dixit
• Human Geography by Majid Hussain
• INDIAN GEOGRAPHY by D R KHULLAR or R C Tiwari. ( both are equally good)

hope it helped.