Introductory or Primer text on Economics?
If you were to read only introductory book in econonomics:
Economics: The User's Guide by Ha-Joon Chang.
It explains all basics concepts in economics, and the differences between the main school of thoughts. It is quite easy to read, it is not a textbook.

For an overview of financial markets:
Capital Ideas, and Capital Ideas Evolving by Peter L. Bernstein

For your interest in electricity:
The Grid: A Journey Through the Heart of Our Electrified World by Phillip F. Schewe, very interesting on how the grid came to be.

Smart Grid: Integrating Renewable, Distributed &amp; Efficient Energy
by Fereidoon P. Sioshansi (Editor), Sioshansi is a reference in Smart Grid and the paradigm change from consumer to prosumer.

Renewable Economics: How to compare the costs of different technologies:
Energy Technologies and Economics