現役東大生が書いた　地頭を鍛えるフェルミ推定ノート　(Fermi Estimation and Thinking Skill workshop)

Written by 東大ケーススタディ研究会 (Tokyo university case study workshop)

It features detailed methods of the Fermi Estimate.  It is very practical and contains lots of exercises which are mostly themes of everyday life.

 

MBA 戦略立案トレーニング (Corporate Strategy Training)

Witten by Tsutomu Harada

This is an excellent book.  However, it features high-level exercises.  If you work on it seriously, you will gain knowledge for sure.