Assalam-o-Alikum.
Dear Friends i would like to add a weblink besides these books.As you know physical geography is more conceptual than committing to memory so images and in depth info are very helpful to prepare for this one.
http://www.geology.com
I have found this site very interesting and informative that will be helpful for you not only in geography but also in G.K paper.It has enough info to quench your thirst of knowledge.
Wish you all the best.
Gladiator