Since couple of weeks there are very many threads on refunds.
Buyers asking refunds ...
Serial refunders ...
Paypal won't help with digital products ...
Scammers buy and asking refund with distributing pirated copies ...
(3 years back I was in the same position when I was not selling my software with a license code or encryption and my script was translated into japanese and was sold by a person illegally. So I did a research back then and saved few urls to use for myself. I was just posting here, if they can be useful to anybody.)
These sites take digital signatures from your buyers.
Digital Signature Electronic E Contracts Sign SignatureLink
Electronic Signature Service | PRONTO Online
Electronically sign your documents and forms online using digital signature software from Yozons
Digital Signature & Electronic Signature Software Solutions - E-Lock
Digital Signature and Electronic Signature resources from E-Lock
Legal Significance Of Digital Signatures LAW INFORMATION
You can keep a Refund policy - "This is digital product. No refunds are offered because of the nature of the product. Purchasing our product means you understand above statement." or something similar. Get a digital signature.
Sure this have other drawbacks like legit buyer get suspicious that 'what if I really don't like this product and with this no refund policy?'. Way around can be - Try to give free first few chapters or few day trial before they purchase ...
Note: If the peson goes for a chargeback, you can producr this legally signed document to your payment processor and the bank that charging you.
I don't know ... just I want to share what I was thinking few years back.