Bill Warren recommends War Eagles: The Unmaking of an Epic by David Conover and Phillip J. Riley, available in both hardcover and paperback from BearManor Media.  Bill writes:

Merian C. Cooper had a busy and productive career as a movie producer all through the 1930s, but his personal favorite remained King Kong; he loved the gigantism of the whole thing, the astonishing imagery. Toward the end of the 30s, he was at MGM, and envisioned a giant eagle with a Viking for a rider, perched atop the Statue of Liberty. Hot damn. He roughed out a story, apparently with historical-fiction novelist Harold Lamb, engaged Willis O’Brien of Kong fame to handle the extensive special effects, which would include a lot of stop-motion animation. The screenplay was written by Cyril Hume, who some 12-15 years later wrote Forbidden Planet. The book includes lots of production drawings obtained from many sources, including a couple of frame blow-ups from the test footage that was shot. These frames are in Technicolor; Cooper, a major backer of the process, was eager to shoot this big movie in color.

The story is somewhat cornball, and the hero (Slim) is very cornball–an eager test-and-military pilot who’s scared of girls–but the script makes the movie sound nothing less than swell, in the glorious old meaning of that word. Slim crashes in Antarctica, in a valley warmed by volcanic heat. Here he discovers the descendants of a lost tribe of Vikings, who speak English, more or less, and fly about on giant eagles. They are periodically menaced by a few dinosaurs. The tribe has a bard who sings legends in what reads like a cross between the usual form “Beowulf” appears in and “The Song of Hiawatha”–but, by George, it works. The climax: a suspiciously Germanic Evil Nation from Europe has developed an engine-killing “death ray” (and engines invulnerable to it); they launch an aerial armada to attack New York, disabling all American aircraft. Slim learns of this and leads his Viking companions to defend New York from the aerial menace–on the backs of giant eagles. Wow.