This is a delightful read! The tale reminds me of those old-time chase movies because the action goes and goes and goes. The characters (many) explore, get lost, are captured, escape, and the sequence repeats. Meet David Innes and Abner Perry who drill into earth's interior to discover a world within a world, Pellucidar. Inhabited by cave men and beasts of the time, they find themselves stranded. David falls in love with Dian the Beautiful and Perry invents and invents. The adventures of Innes and Perry combine with those of several other characters. It's great fun to read!