Dear likeyou,
I'll walk around Popular bookshop tomorrow and revert back
to you. Your son is Sec1 NA this year. 
As for the Primary 4, I'll ask my colleague for
recommendations.
Best Regards,
Chin Seng
Hi Chin Seng...thanks for your help. When I step into the popular
bookstore and wanted to get a assessment books for my kids, but
dont really know which author is suitable for the students. Not
wanting to buy a thick book, just a thin book that can make my kid
do a few pages per day.
Once again, thanks ya and am waiting for your reply.