One ruleset I immediatly rebought after getting back in the hobby, and I must admit, finally read through decently, is Black Powder.
Produced by Warlord Games (if you order it directly from them, you get the highlander from the cover as a bonus), this details the wars fought in the late 18th until half of 19th century.
Now, the one thing Black Powder does seem suited for, if not specifically written, is big battles on huge tables with a few players on each side. If you want to play with your mate on a standard 6x4 table, the maximum move of 36" would put you straight in his deployment zone after turn 1... and cavalry somewhere behind the table even. Granted, it`s a lucky roll sequence to pull that off, but it is perfectly possible.
On the other hand, IF you have access to huge tables and players (like, in a club or such), these rules can give you a pretty big, 3 brigades of 4 - 5 regiments each per side, battle that can be finished in an evening. Covering the period from around the Age of Marlborough, over the Napoleonic wars and past the American Civil War into the Sudan, you get some nice basic listings for playing.
In the meantime there have appeared supplements for most of those periods (I shared my thoughts on the ACW expansion, Glory, Hallelujah!, a while ago) which expand given era's further, this book allows you everything to game with.
Produced as a hardcover, with nice glossy pictures of figures in action and thick paper, this is a truly magnificent tome of a rulebook!