Winston Groom (Jeff Roberts/AP)

Winston Groom, author of the new must-read book “Shiloh, 1862,” will speak at National Geographic on Thursday at 7:30 p.m. If he is anywhere near as good a speaker as he is a writer, this will be a terrific evening for anyone with an interest in the Civil War.

Groom, author of eight fiction and seven nonfiction books, has given the Battle of Shiloh the mega attention that it deserves by writing a book with the storytelling appeal of fiction but solidly backed with fact.

Shiloh, also known as Pittsburg Landing, was fought on the Tennessee-Mississippi border just north of Corinth on April 6 and 7, 1862. The spring that year was much like the one here in the Washington area now, with a burst of flowering trees, blue sky and pleasant weather. It should have been gloomy and nasty because, by the end of two days, close to 3,500 men had died, 16,000 were wounded and more than 7,000 were missing.

Groom doesn’t ignore the military aspect of the battle, but the terribleness of war, and particularly of that battle, is brilliantly told by some of the victims, both civilian and military, who experienced the fighting, what the author called that dreadful something that descended on them “as swift and merciless as a cyclone from the southern plains.”

There is little Elsie Duncan, whose father was the minister at the log Shiloh Chapel and the drill sergeant for the local recruits. The battle raged in front of their house, leaving in its wake “dead men and horses.” Inside the house, “the floor was covered with blood” where the wounded and dead had been brought.

Gen. William Tecumseh Sherman, long before he became famous for his destructive marches through the South, was a principle player at Shiloh. Here he is the buffoon who inexplicably turned aside a dozen reports of Confederate armies heading for the Union camp. He called those reporting to him “scaredy-cats.”

Leander Stillwell, an 18-year-old Union corporal, stood in line waiting for the enemy to appear. He thought of his old log cabin back in Illinois and his father and mother, “who would be getting my little brothers ready for Sunday school, the old dog lying asleep, the hens cackling about the barn.”

There are many more real people telling their stories thanks to massive research on the part of Groom.

At the end of the book, it seemed odd to be back in the world of 2012. The feeling is like leaving a theater after a particularly terrific movie and blinking in the bright sunlight, not quite able to throw off the mood.

This is a book that will stay with you for a very long time.