Offworld will need to obtain ISBN numbers (Your Book’s Unique Code)
so sales and rights can be tracked globally. 
 
Free?
If you intend to retail eBooks and Paperback books exclusively on Amazon, Amazon will provide ISBNs for free. If you intend to create a hardback book, Amazon does not handle this so an ISBN will be required.
 
In your Name
All ISBNs acquired under this Service will be registered in the Author’s name. 
 
Random Numbers
It is not possible to choose specific ISBN numbers. They are generated by the provider.
 
Discounts
The global provider of ISBNs operates a comprehensive discount for multiple orders.