I think it’s very inspirational; I find Jim Al-Khalili to be a very inspirational science educator.
Credibility-wise, I have to place it in somewhat of a belief system though. This doesn’t make it wrong by any means; but rather, it is science fiction supported by some heavy mathematics.
Yet, being speculative or fictional does not make it a bad thing at all; if it inspires people to consider deeper things… to see the complexity of their own selves and find some kind of deeper core that is meaningful and connects us all together, I see nothing wrong with it.
It serves a societal function; providing the missing religious/mystical/spiritual link between us and the Universe that used to be fulfilled by older religions and it carries with it the authenticity of being well thought out and mathematical along with inspirational.
So, all in all, I think it’s a good pursuit. It’s good for society, good for people. It gives us hope that one day we might just have the answers, and fills our dreams and imaginations of things far larger and far smaller than we can experience anywhere else but the imagination.