It is difficult to give a list of "even handed" historians when the standards of subjectivity aren't clear.

No historian is completely objective. The problem is that basically all respected historians I can think of do not follow a simple "pro-Northern" or "pro-Southern" slant. Their views vary in any number of ways.

There are numerous books and articles about sectionalism and the Civil War that are very good. (Whether they are "even handed" between the line of "pro-North" or "pro-South," I don't know because such division is very unclear and historians don't work within that type of model.) Here are a few off the top of my head...

William J. Cooper, -The South and Politics of Slavery
Fehrenbacher - The Slaveholding Republic
Eric Foner - Free Soil, Free Labor, Free Men
Lacy Ford - The Origins of Southern Radicalism
Eugene Genovese - Fruits of Merchant Capital
Michael Holt - The Political Crisis of the 1850s
Michael Holt - The Rise and Fall of the Whigs
Oakes - Republicanism and the Old South
J. Mills Thornton - Politics and Power
Bertram Wyatt-Brown - Southern Honor
William Lee Cooper - Arguing About Slavery
Chandra Manning - What This Cruel War was Over
Allan Nevins - The Ordeal of the Union series