Paul O’Connor observes that even if it shouldn’t be judged by its cover, this book is good reading nonetheless. Reviewed by Paul T. O’Connor THE WAR THAT FORGED A NATION: WHY THE CIVIL WAR STILL MATTERS. By James McPherson. Read by Grover Gardner. Audible.com. 7 hours and 29 minutes. $19.95. You have to be careful…