This isn't so much a history or a biography as a hagiography. In the introduction Hayman makes his close relationship with Soult's family clear and while this obviously helped with access to the Marshal's papers it does feel like he has fallen under Soult's spell.
In practice this means that every part of the story is given the most positive possible gloss. Soult can do no wrong. Every incident is explained to make it clear that Soult's motives were pure and his plans were defeated by the inaction or incompetence of others. Hayman makes the case for Soult as one of Napoleon's most significant and talented marshals, and it more convincing if he felt more even handed in his approach.
As it stands this feels like special pleading, out of kilter with much of the rest of what has been written (at least in English) about Napoleon's marshals. To truly 'correct the record' as the author clearly aims to do it would need to engage more critically Soult's record.
In short a reasonable brief introduction to the life of one of the more significant marshals, marred by an uncritical approach.