John Rossi, Professor of History at La Salle University cites Put Out More Flags as underrated, while nevertheless being considered by some as the best novel of WWII. This is in the latest issue of the American Conservative Magazine. Rossi describes the novel as:
 …a seminal work in the transformation of Waugh from the author of savage satires about the “Bright Young Things” of the late 1920s and early 30s like Decline and Fall, Vile Bodies, Black Mischief, and Scoop, to the more sober novelist of the postwar crisis of faith. It’s filled with the characters who once trotted mindlessly through those books, the “wealthy ill-mannered louts whose action left havoc in their wake,” men like Basil Seal, Peter Pastmaster, Alastair Digby Vane Trumpington, “Bright Young Things” all. It is also the novel that foreshadows the more serious postwar world of Charles Ryder in Brideshead Revisited and Guy Crouchback in Sword of Honor. As such, Put OutMore Flags is worth a second look.
He goes on to discuss in greater detail the development of many of the characters from the  the early novels into more mature individuals in the early days of the war. He focuses particularly on the women in the novel;
Basil’s batty sister Barbara; his lover Angela Lyne; and Sonia Trumpington, Alaistair’s wife, all in Waugh’s phrase part of the “wreckage of the roaring twenties.” They all are sketched affectionately and with warmth; no longer the brainless females of his earlier novels, they are key figures whom Basil’s, Peter’s, and Alastair’s lives revolve around.
He also discusses the novel’s context and its publication at a crucial point of the war. There are discussions about the major characters and how they evolved from the earlier novels. And he notes Waugh’s references to other literary figures of the day in characters such as Parsnip and Pimpernell. The essay is well written and contains several original insights. It has already been cited and recommended in the Prufrock column of the Weekly Standard magazine.