Would this be Offensive?

I don't know about offensive but it would probably be awkward

I mean a religious person would probably already have a bible so who else would you give one to 😹

It would depend on the context in which the gift was sent. Imo

It might seem a little bit like you're dropping hints to try to convert them... I got a very nice Bible upon leaving my school, although like I say, it's a bit different when it's a school compared to whether it's one person.
I wouldn't do it personally. Buy another nice book. The Folio Society does a lot of very nice bindings.

Not offensive, just not a thoughtful gift.

Yes it would be very offensive

Well, what's the message you're trying to send? Like is it a conversion attempt? Are you hollowing it out and hiding something inside?

nope..