I am a high school student who will be entering college in one and a half year (It is so long though).
For me, Mathematics primarily means Number Theory. My interest in Number Theory always motivates me to go and take a look at those wiki articles which are not really discussed in classic or even modern books.
For instance, while studying about prime numbers, I found many things not specifically discussed in books. Some of them are Legendre conjecture, Prime gaps, Mills constant etc. I am confused whether I should keep studying these things which authors don't dare to discuss or follow the patterns of books instead.
For your kind information, I would mention that I frequently use NZM along with G. H. Hardy's
Introduction to Number Theory sometimes. For problems, I often do UC Berkeley's online assignments.