Jens Carstensen has taught mathematics at high school/college level for over 40 years in Denmark. He is the author and co-author of several successful textbook systems and is currently continuing this work. He has been the editor of a Problem Corner for 40 years and has published and edited a small mathematics magazine, thereby obtaining a wide experience of writing mathematics for both students and professional mathematicians.This book is a very well written introduction to the geometry of the triangle. It takes the readers through the theory in a leisurely and transparent manner and carefully pre- sents the theorems and proofs.