What should I do if kids keep asking us to buy things (toys or books) for them which I think it is unnecessary? For books, I can bring them to library. For toys, once 1-2 month is ok. Will they become shopaholic like me when grown up if I too control them lol?

How old are they? If they are receiving pocket money, you can consider teaching them how to save up a portion of their pocket money and bring them on a shopping trip at the end of the year to get the items they want (especially for toys). For books, you can come up with a reward system such that they can be "entitled" to a new book once they achieve certain criteria. Just some suggestions, so that they will learn that they have to "work" for the things they want. Haha.. just my humble suggestion on how to introduce them to the "harsh" reality of the world. ;p