https://www.reddit.com/r/AskHistorians/wiki/books/innerasia#wiki_general

the wiki has some book recommendations on the mongolians

While not Ghenghis, I highly recommend this book https://www.amazon.ca/Leadership-Secrets-Attila-Wess-Roberts/dp/0446391069/ref=pd_sim_14_1/145-1957454-0178362?_encoding=UTF8&pd_rd_i=0446391069&pd_rd_r=4bbe7eca-758b-11e9-a70e-fdfd69152f1b&pd_rd_w=1QFCg&pd_rd_wg=kf141&pf_rd_p=29a85b27-a36a-4f8d-94ca-61aa962c5f39&pf_rd_r=PCP8R1F0CTCH9B83CXC2&psc=1&refRID=PCP8R1F0CTCH9B83CXC2 Its a very neat book written from the perspective of Atilla the Hun by the author. There are similar books written by authors from the view of Ghenghis.

https://www.amazon.ca/Leadership-Secrets-Genghis-Khan/dp/0593058488