Edgar Rice Burroughs wrote his seven-book Pellucidar series from 1914 through 1944. I have the first two in book form from Dover Publications, but the other five are eBooks. They are available from Roy Glashan's Library. It is in Australia because apparently they are still under copyright in the U.S. Mr. Glashan has prepared the eBook editions. They are available to read online or on an eReader other than Kindle. (It appears they are not in that format at this point.) However, Gutenberg Australia has some free converter tools in their Help section to convert text or HTML files to both EPUB or MOBI (Kindle). I have not tried them yet, however.
There is a discrepancy between Wikipedia and Mr. Glashan as to which book is the last in the series. There are arguments for both sides. The final two books, Savage Pellucidar and Land of Terror, consist of short stories rather than one novel. The first three stories of Savage Pellucidar were published in 1942, but the final one was discovered by Burroughs's son Hulbert in the early '60s, and published in 1963, technically making it the last published. Land of Terror, however, was chronologically most likely the last book, published in 1944. However, as far as the story line, Land of Terror chronologically follows Back to the Stone Age. Savage Pellucidar is set apart, in that it really doesn't follow the story line of the previous books. It is more a continuation of Book Two.
In 1976, Eric Holmes published another Pellucidar book, authorized by the Burroughs estate called Mahars of Pellucidar. Another book, however, Red Axe of Pellucidar was ready for publications in 1980, but blocked by the Burroughs estate. It was finally published in 1993 in a limited private collection. These two books are not included on this page (at least for the time being.)
Edgar rice Burroughs lived from 1875 to 1950. He was born in Chicago and died in Encino, California. He is buried in Tarzana, California, an "affluent, highly educated neighborhood in Los Angeles" and named for Burroughs's most famous character.
Here are the seven books, which you may click for my review. The first two, as mentioned are from Dover, but for the other five, I found the images of the original dust jackets on Wikipedia, which I think are very cool. The whole series, in fact, is quite cool, lots of fun, and filled with daring adventures and romance. Highly recommended reading!