I have said before, and believe, that up until the past few hundred years (in The West) religious claims can nearly always be taken as true - so long as we pay careful attention to the specifics of those claims.
This is because in the past the great mass of people would not make any religious claims that they did not believe to be true; because for them religion was real, and it was existentially and permanently valuable to tell the truth and hazardous deliberately to lie about the core aspects of religion.
So, no religion except Christianity offers its adherents anything as good as, or better than, an eternal, perfected, bodily resurrection dwelling with the deity after death; and so far as I know, none ever have done in the past 2000 years.
We moderns might imagine it would be easy to offer something better than Christianity, or make the same offer on 'easier terms' - but that hasn't happened among - and indeed most religions offer a great deal less, and often enough offer something pretty horrible.
This is evidence of their sincerity, and I would say truth - in the sense that they are saying 'If you follow this religion, then this is what will happen to you' (within limits of mortal expression and comprehension - so nothing stated in public discourse can be taken absolutely literally as the whole truth) - and I think this is broadly correct. Do this, and this will happen.
Clearly this does not apply to modern times, because many people so profoundly disbelieve in religion that they regard themselves as free to say anything - including whatever lies and misleading comments are expedient in the short term. We live in an era when - for many self-identified Christians - Christianity, for such people, is 'just words'; and they will say and write whatever they regard as most necessary or useful to advance the - usually socio-political - cause which is their real belief.
When it comes to the Bible it is interesting to notice that of all the authors and sources in the various books of the Bible - only John in his Gospel claims (not explicitly, but clearly communicated) to have a full understanding of the reality of Christ and his teachings.
And it is also noticeable that John explicitly states (towards the close) that he has not been able to express this full understanding in the Gospel itself.
None of the other Gospel writers claim this (I don't think) - nor does the Apostle Paul. Nor does John himself in the Book of Revelation (which is presented mostly as a vision - indeed a glimpse, hence to be taken symbolically).
I regard this as a confirmation of the primacy of the Gospel of John in the Bible - and support for using this Gospel as a key to understanding the rest of that large and complex book.