Rules of Generating book ID

It is tentative. I don’t think I will label my books. It was originally motivated by being able to find a book more easily. But it seems that I remember where to get a book when I need it.

1. Category code + Number
2. Number was origionally assigned as the rank of the book in its category devided by 100 (i.e rank/100)
3. For new book
   1. search for the maximum number in that category (mn)
   2. use mn+0.01 as number for the new book