The golden people Book

The planet was called Golden in honor of the planeteer whose ship had crashed there years before. It was an Earth-type world, with humanoid natives, and other creatures that were--something less. Or maybe more, for almost all of the planet was covered by an invisible Field which blanked radar, damped the power of the Earthmen's stunners, immobilized their robots and caused watches to run backward. No machine or weapon more complicated than the lever or knife could work inside the Field. Which meant that the Space Force had to revert to the primitive to explore the world of Golden. And obviously, someone or something hidden in the vast reaches of the planet had planned it that way. . .