When my sister and I are roaming around the city, this caught my attention on one of the stores we went into and bought it right away. I got one for her and another for me.
Since I have plenty of books compared to her which means I have a lot to study and topics to cover, mine were gone after a month or two. She offered the half of her part to me but my need for it is much higher than hers so in the end she gave me the other half.
Lesson of the story: if you like something and it is one of your needs in the near future you better have it, enough to sustain your demands. Law of Supply and Demands applies.