I am not sure about the best or least biased - how can one make such a judgement?
If I was on a desert island the books I would take from by own library would be, in no particular order and for a variety of reasons.
1. Elting/Esposito - Atlas of the Napoleonic Wars
2. David Chandler - The Campaigns of Napoleon
The above are the basic primers for overviews of the wars in English.
3. John Elting - Swords Around a Throne: Napoleon's Grande Armee.
4. Peter Paret - Yorck and the Era of Prussian Reform 1807-1815
5. Gunter Rothenberg - Napoleon's Great Adversaries: Archduke Charles and the Austrian Army 1792-1814
6. Richard Glover - Peninsular Preparation: The Reform of the British Army 1795-1809
More primers but this time oriented to the armies in question. Nothing in English like these on the Russians unfortunately.
7. Henry Lachouque/Anne Brown - Anatomy of Glory: Napoleon and his Guard.
Mainly for nostalgic reasons as it is the book which started it all for me and the pictures are worth it, even if the text isn't.
8. Sir Charles Oman - Wellington's Army 1809-1814
Because I can't take his History of the Peninsular War.
9. Tim Blanning - The Origins of the French Revolutionary Wars.
The most entertaining single volume of the prequel to the Napoleonic Wars I have read and which makes a lot of sense - to me anyway.
10. Scott Bowden - Napoleon and Austerlitz.
To light the fire with and for other purposes. :-)
I'd also like to take Jimi Hendrix Electric Ladyland and a CD player with an unlimited supply of batteries, so I can play air-guitar on the beach as the sun sets, after consuming vast quantities of the brew I will make from tropical fruit, seaweed or whatever comes to hand.