There's one called "Secret Boys Business" by Faye Angelo and two other people - they are primary school teachers and the book is really age appropriate and informative. Check in your son's school library, chances are they have it.

Another one is "Secret Men's Business" by John Marsden. It was incredibly popular years ago as being THE book for boys but if you go down this path, it might be worth reading it yourself first to see if it is age appropriate for your DS. I think it might be aimed for boys a little older.