Book recommendation (in german languaga only)

Saving energy affects us all - especially at this time of year. Prof. Dr. Maximilian Gege has published what I think is a very recommendable book. Very practice-oriented answers to questions that concern us all.
How can I reduce my energy consumption? A guide worth the money. Available in any bookstore or online.

The proceeds from the book are used to support the foundation "Chances for Children". A great project