Have you read the book? - it is basically a day by day factual account of what happened to the Guards, by an eye-witness, published very shortly after their return to Britain. He generally sticks to what he saw himself and was told in general orders and the facts reported are supported by other contemporary accounts. I don't think that the overblown language of the dedication (typical of the period) detracts from its value. It is much better than the memoirs, often published years after the event, by prominent figures with an axe to grind or a reputation to defend.
I'm not really sure I understand what you mean by "it's always invaluable to see what the other side has to say"