According to my research, it seems that based on Shia scholars, keeping/studying such books (like Bible and so on) is haram. Because Bible is not the words of Isa (Jesus), meanwhile, during many centuries, the distorted Bible doesn’t conform to the reality. So, it can be a kind of distorted book which is not the right one.
Hence, buying such book(s) for everyone can be deemed as if you are helping him in starting/following wrong way, consequently, logically and canonically (based on Shari’) you’ll be partner of that (helping in misleading …)
Regarding 2:256, there are long explanations about that, but I strive to point it out very shortly (based on my mediocre knowledge). Actually, this verse’s concept can be this that:
Choosing the religion is not compulsory and actually it is done by the free will of the humans, but if we want to suppose ..., then creating heaven and hell would be a profitless act, and bringing us to this world (to testing) would be useless (and Allah would take us directly to the heaven without any testing).
As an example (I made it as a related example):
E.g. logically, you can pass the traffic (red) light (by your free
will), (and is not a compulsory issue for you to stop behind that,
because you have free will to stop/pass, otherwise you’ll be punished
then for choosing the wrong way (passing the red light) by your free
will. (God willing, my explanation/example can convey the concept of
You ought not to buy such book(s) for anyone, since it can mislead them in the wrong way, and you’ll be a sort of partner in that helping. (And I assume your act can be a kind of confirming his wrong decision/act too). Good luck.