In what normal forms is a simple DB, why, and how can it be maximally normalized?

[Math-IT-Lang]

You can use out_of_stock field if you want but the risk of it getting 'out of sync' with actual data is a consideration. Whether or not a book is out_of_stock could be calculated when needed. Review http://allenbrowne.com/AppInventory.html

Thanks for the tip. The question was: in what normal forms is the originally proposed database (... NF3, BCNF, NF4, NF5, etc.), why and why not is it in the following normal forms?
It seems to me that the web address you sent is virused.