Physical geography by De Blij
Book of Sarfraz Bajwa (can't recall its name right now)
These are vital for the preparation and they cover almost all the topics.In addition, there are two books of geography by Jahangir Sons. They come handy in the last days as they contain outlines of all the topics as well.
Don't confuse yourself by collecting several books. A dedicated study from two or three books could help you more than piling up books which you can't study simultaneously!
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