I have purchased a book on Amazon and it was shipped to me. On the front page of the book, it clearly stated:
Circulation of this edition outside the Indian subcontinent is UNAUTHORIZED.
I live in the US and this book is clearly shipped out of the Indian subcontinent. The book condition is not new but used (like new). Am not sure if this purchase is illegal and what I should do about it.
You're probably fine. There's three points here that might commonly be governed by copyright law: the export from India, the import into the United States, and the sale of the book (generally it's the seller and not the purchaser on the hook). You're not the seller, and you're also probably not the exporter so import is the only thing you would need to worry about.
Likely Amazon is the importer, however, some quick searching around led me to a Canadian Amazon page which made clear that there are instances where you would act as the importer (I'm unsure if there's an equivalent US page).
Under US law, import and even resale of a book made lawfully according to US copyright law is legal. This is true even if that book was manufactured overseas, as the Supreme Court expressed in Kirtsaeng v. John Wiley & Sons, Inc..
I'm less familiar with Indian copyright law, though since copyright law is usually territorial, it's unlikely that your US-based actions would be in violation of Indian law. However, it's entirely possible whoever sold/exported the book is in violation of Indian copyright law.
Indian courts have interpreted the first sale doctrine to be territorially limited. So, for this book, second-hand sales are allowed only in the territory where the copyright holder originally released the work and it can only be sold outside that territory with the copyright owner’s permission.
Technically, the book you have in your hands is a copyright infringement. However, the seller is the one who made the infringing copy, not you.
