I've been very intrigued by the people surrounding Napoleon especially on the battlefield and would love to get an idea of what Napoleon thought of them. I've come across a few comments Napoleon has made about his Marshals but was looking for a source that would cover all of them (or at least most), providing as much detail as possible. Where would be a good place to start? Any books?
The obvious choice here is Napoleon's Marshals. It's a collection of essays on the Marshalate, edited by David G Chandler. Each essay is an external look at each Marshal, how and why they earned their baton and what they did afterwards, and also includes a battle where said Marshal was notable (if not necessarily successful - the one on Marmont, by John L Pimlott, looks at Salamanca). Each essay also includes more books for further reading on that Marshal, if You'd Like To Know More. It also collects what may be the comments you've seen of Napoleon speaking of his Marshals. If they are, they bear treating with some caution. These comments were made after he was exiled to St Helena, and are thus coloured by the "circumstances of disillusion and bitterness" that prevailed there, to quote Chandler from that section.
Aside: For 'favourite Marshals' based on the book, I'd say militarily Davout has my vote (Auerstedt earned him his place in history all on its own), but personally I have a soft spot for Macdonald. Also, honourable mention to Lefebvre and his wife Catherine - I'm a sucker for stories of marital harmony no matter the era.