While Andreescu's books are highly recommended, students often compare them to other legendary texts:
The problems are likely to range from moderately challenging to very difficult, catering to students who are preparing for or participating in mathematics competitions, or simply to those who enjoy solving challenging geometry problems. titu andreescu 106 geometry problems pdf better
Titu Andreescu has made significant contributions to mathematics education, especially in the areas of algebra, number theory, and geometry. His problems are known for their creativity and for requiring deep understanding and insight. While Andreescu's books are highly recommended
Depending on your current level and goals, these books are often considered superior or essential supplements: Euclidean Geometry in Mathematical Olympiads (EGMO) especially in the areas of algebra