ISBN Number

I want to add a new feature ISBN no for the product( which are books in my case), which will be different for each of the book. I can see that attribute which can be added need a drop down list, but there is no option of adding the attribute whose value can be added by admin , and is different for each product.

Try using the product variant give it a name like ISBN 111-444-123445, then change the product template to 'Variants in Grid' and you will see the ISBN etc below the product description when you view the book in the store. This is just the easiest way I could see to do it, there will be other options.