I am an emeritus professor of mathematics. Recently my book titled "An Alternative Approach to Lie Groups and Geometric Structures" is published by OUP. For more than 30 years I searched for a "good" definition (good meaning simple and intuitive) of a geometric structure and its curvature. This curvature should measure the "deviation" of this geometric structure from the "fully symmetric" models which are certain homogeneous spaces. Furthermore, any homogeneous space is some fully symmetric model with vanishing curvature. For instance, in Riemannian geometry, there are 3 fully symmetric models: constant curvature = +1, 0, -1. This book is the outcome of this endevour. This project is far from being finished and is waiting for new contributers as I have come to the limits of my scope! :-)