Way back before I went on vacation last week, I seem to recall reading Edgar Rice Burroughs' 1914 book At the Earth's Core. This is the first book in Burroughs' Hollow Earth series, the second of which I uncharacteristically read first. Obviously that didn't trip me up much since I give a pretty solid run down of the plot of this book in my review of the second book. The only thing I can really add after actually reading the first book in the series is that adorable tiny little whales live in some of the ponds on Pellucidar, but that doesn't stop our hero from catching them and eating them raw when he is on the run from the freaky lizard rulers of the inner-earth kingdom.
Like much of Burroughs, this is a fun and dated sci-fi/adventure novel, but if you like that kind of thing (and I surely do), then you can't go wrong with the manly hero, freaky creatures, and staunch early 20th century American idealism of this series.
[My copy (which features the cover pictured above) is a 1976 Nelson Doubleday Book Club edition, produced to accompany that year's film of the same name. To make it even sweeter, it features 8 black and white photo stills from the movie, which starred Peter Cushing and Doug McClure (half the namesake of Troy McClure, who I'm sure you remember). And if you can't get your hands on your own copy, then read the whole thing online here.]