I'd begin with Napoleon's Infantry Handbook by Terry Crowdy, this is a very nuts and bolts approach to the workings of an infantry regiment and the daily routines and experiences of the life of a French soldier. By the same author there is Incomparable: Napoleon’s 9th Light Infantry Regiment which is a detailed history of a single infantry regiment, but benefits very much in that one of its enlisted soldiers left a detailed account of his life (which is a rarity compared to the number of accounts left by officers). Napoleon's Men: The Soldiers of the Revolution and Empire by Alan Forrest is an amazing compilation of the writings and experiences of French soldiers.

For the British army there is All For the King's Shilling by Edward Coss which examines the campaign and combat behaviour of British soldiers. There are numerous regimental histories for British units during the period - I'm partial to Redcoats against Napoleon : the 30th Regiment during the revolutionary and Napoleonic Wars by Carole Divall and Dragon Rampant: The Royal Welch Fusiliers at War,1793–1815 by Donald Graves.

Marching, Fighting, Dying: Experiences of Soldiers in the Peninsular War by Gareth Glover collects the recollections of soldiers of all armies during the Peninsular War.

For the Russian army, sections of Soldiers of the Tsar: Army and Society in Russia 1462-1874 by John L. Keep cover the common soldiers experience, but it is a broader work and not specific to the Napoleonic period. From Serf to Russian Soldier by Elise Kimerling Wirtschafter is more narrow, focusing mainly on the transformative process of turning a peasant into a soldier.

Other armies unfortunately don't have much coverage, in English or otherwise.

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