Mathematics is my favorite subject in school days. I deals with quantity, structure and space
I like geometry but not algebra.  What is your favorite math?
I like both geometry and algebra in mathematics 
Is calculus a good subject to learn?
Yes Definitely it is the good choice to learn and one of the important structure in mathematics subject
Can I learn math subjects just by reading a book or do I need a teacher?
You can learn by your own but you can get everything you need by using textbook. You can understand the mathematical reasoning better from a teacher