you can follow any high school earth science book.
you can download softcopies from here:- tinyurl.com/iesopreparation
I am Amarjiit Pandde, Silver Medalist - IESO 2016 held @ Japan. As it is supposed to be just a few lines i won't beat around the bush and get directly to the point. I am passionate about Earth System Sciences and i have made a website for IESO preparation
(www.tinyurl.com/iesopreparation ). I and Keshav will be posting quite a few things which either are important for IESO or are fascinating but in the domain of Earth System Science.
Stay TUNED !!