Once An Eagle is conceivably only for old hawks and the Book-of-the-Month Club. Twice as long as Myrer's Big War, it's a seemingly interminable bivouac from World War I through World War II and after. Slogging through stretches of mud, blood and guts is Nebraskan born Sam Damon, a man of indomitable conscience and undeviating conviction, although he is finally trapped in a philosophical pincer action can a good soldier be a good human being? War (I) first costs him his oldest friend and ""bunkie"" who buys ""the whole wad"" in France, telling him he's wrong; his wife, Tommy, always resentful of the Army, never forgives him for his lack of pay and promotions and finally the death of their only son in action (War II); while Sam, in between arid army post life, chasing through the wilds of China and dodging Japanese patrols, finally serves throughout in the Pacific. But when last seen, at 65, he dies this time blocking his old enemy's hopes of invading China. Myrer, an overwriter, could have used the discipline which is innately Sam's; in the distention of purple prose Purple Heartburn.