I was asked to transfer a book via airplane

I am with commenter Aganju here. In some countries this kind of things is completely normal, even among complete strangers. And in plain view of custom officers. I think it depends a lot on the level of mutual trust within a society vs. the availabality of other modes of sending (small) packages quickly.

It is also a situation I have been involved in quite regularly. Both as a sender and also as someone carrying stuff for other people. For some countries, sending e.g. important documents or medication via mail is simply not a good idea. And of course this is also cheaper and quite fast. So I personally do not see how this situation should be suspicious from the outset.

On the other hand there are some reasons to be careful. You apparently do not know India very well (or at least not well enough to know whether this is common or not). Stuff may break or get lost on a flight, and you may not want to take that responsibility. Organizing the pickup may be time-consuming (from my experience, this usually involves phone calls and some waiting). And of course you should also be careful about stuff that you cannot check yourself, e.g. packaged goods. But I personally probably would not be too concerned about a book.

Sure, there is some additional risk involved in carrying stuff for others. But the same is true for sending stuff this way. The carrier might lose things, or he might ask at customs if they think the book is legit. I wonder what could possibly be in a book that makes this higher risk of loss or detection outweigh the risk involved in carrying the book through customs. On the other hand you might also wonder how a book is worth asking a friend of a friend to pick it up and carry it for you. Is it in Romanian and are Romanian-language books hard to find in India?

Basically, if you carry the book, you have a certain risk that you are used for something illegal. If you do not carry it, you risk being considered unhelpful or at least (if you are a foreigner) slightly culturally insensitive. For me personally and for some countries I know (not India), the second risk - as a function of severity and probability - outweighs the first one, but that is a decision that you must make for yourself.

Just a different view here.

During floods in Kerala, India, I was in Singapore. There was a high problem of clean water, especially in rural Kerala. So, we friends met and found a high volume manual water filter that is found by a startup in Singapore. Problem is sending via mail or courier. It will take too much time to clear customs and by the time it reaches there, utility would be over.

So, checked and sent via a friend's friend who is going to Kerala and sent via him. Purchased at noon, at night it was in Kerala and from morning, it helped a lot of families access to clean water in time of need.

So, check the reason, check the story and if you feel trustworthy enough to transport, do that after proper verification. If you don't feel comfortable, feel free to reject. A book which is valuable for them and needed soon is ok, in my personal opinion.

This depends on a lot of things but first and formost it should depend on how much trust you are willing to place in the ‘friend of a friend’ (hereafter FOAF) and in the friend whose friend it is.

If the FOAF is someone I met a couple of times but whom I wouldn’t yet call a friend, if the actual friend of mine is someone I share and do a lot with and if the story in general checks out then I would probably agree. However, there are a lot of red flags that could be raised:

• if I never met the FOAF that’s essentially a no
• if the friend themself is someone I am not overly close with, that’s a no
  (I have friends whose requests I am more likely to deny than others’)
• if the connection to the elderly couple raises even the slightest doubt, that’s essentially a no
  (Why was the FOAF with them? Are they related?)
• if the explanation for choosing a human courier over the mail don’t add up based on what I know about my friend and their friend or if it doesn’t match what I know about their typical behaviour, that’s a no
• if there’s even the smallest hole in the FOAF’s story of why they were in your country, that’s essentially a no

The list goes on and there are more questions that can be asked. Only if you are comfortable with every single answer to all questions that come up you should be willing to agree. The fact that you asked this question strongly implies that you are unsure about at least one aspect and that you should probably (politely) decline. However, I won’t deny that I can see examples where I would agree.

As they say, if you have to ask, the answer is "No".

It's fine to accept parcels from friends (I've done that myself), but only for a definition of "friend" which implies deep unconditional trust.

Imagine you're stuck near that person's house with a body you need to get rid of. You have an explanation for what's happened, but a random stranger will likely assume you just killed the guy for cash and call the police. Would you consider asking that "friend" to give you a hand? If not, there's not enough trust between you to carry items over the border for them either.

Just say No.

It's not your book, so you shouldn't be taking it unless you're being paid as (and have insurance as) a courier - which would be much more expensive than mailing the book. Also, is that book available in India? If so, it would probably be cheaper to buy a new copy.

You don't know these people. You should not be risking so many unknowns for them.