It's very specifically not a holy book because it does not hide any reasoning or ask you to take anything on faith. Quite the opposite - all of his working is shown, every assumption is stated, and you are very explicitly given the tools to calculate and update his work as new advances and considerations emerge. There is a whole chapter on not-the-UK, and how the math changes. The reason the book was such a global success is not because it was a statement of opinion about UK energy policy, but a proper treatment in how to thing about energy production and use, the tools for which can be applied anywhere.