Napoleon didn't have a long life -- he was not far beyond fifty when he died -- but it was a remarkably full one. Roberts's telling of the tale, as can be judged from the title, is aimed at depicting its subject in the best possible light, Given the mix of hatred and contempt with which many biographers, especially English ones, have treated Napoleon, it's a worthwhile exercise, and mostly a successful one.
It's a measure of just how full Napoleon's life was -- sixty battles, two wives, two dozen mistresses -- that even as long a book as this sometimes seems a bit rushed. In particular, many of the man's non-military achievements, such as the creation of the Code Napoleon, one of his most lasting legacies, seem to spring fully-formed onto the page, when in truth they must have involved a great deal of work and debate on the part of Napoleon and his associates. Similarly, Roberts provides virtual laundry lists of things that Napoleon routinely did when he conquered a new country -- building infrastructure, reforming local laws and so on -- in a way that suggests all of these tasks were accomplished within a week by the man himself, which is self evidently not the case.
The military side, in contrast, is retold in great detail. Roberts has been careful to look for sources other than Napoleon's own voluminous correspondence, which routinely exaggerated his successes and downplayed his very few failures. For the most part the descriptions of the battles are clear. However, in the Kindle version, the accompanying maps are very small. If it's important to you to follow retrace the actions for yourself, the physical book would be a better choice.
Many depictions of Napoleon show a glum looking figure with one hand permanently inside the front of his jacket. Roberts paints a picture of a man whom most people found charming and affable, and there are plenty of quotes to show that he possessed a good sense of humour. This will, I suspect, be news to most readers.
Lastly, Roberts dismisses recent controversies over Napoleon's death. He is convinced by detailed autopsy reports prepared at the time, on St Helena, that point strongly to stomach cancer as the cause of death.
In an afterword, Roberts notes ruefully that writing the book took him longer than the total time that his subject spent in exile on Elba and St Helena combined. Time well spent: this will be the standard work of reference for a long time to come.