"Understanding Radio", by Watson, Welch, and Eby. McGraw-Hill 1951.
"This book is written for students who have little or no background in electricity or science".
This book starts out its coverage of "glowbugs" by smashing one open and examining the grid, plate, etc!
It then proceeds thru a series of circuits, starting with the crystal set, vacuum tube diode detector, triode, etc. The 1H4G is used for many of the early circuits. Each project has a "why-it-works" section. To give you a feel for the level of detail, the discussion of the Hartley oscillator takes 15 pages.