This review was written by Oswald Rabbit over at Pinnacle Entertainment Group, "I strongly recommend The Gilak's Guide to Pellucidar by David Critchfield, published by Darel Az Books. It contains everything you could ever need to run a Pellucidar-based campaign, including maps, plot summaries of all the books, descriptions of characters, places, and creatures, and tons of background info about the Hollow Earth milieu and other non-canon material available online from various fan sites and authors. Indispensable!"

David Critchfield’s "A Gilak’s Guide to Pellucidar" is a book about books, a top-notch guide to the seven novels that make up Edgar Rice Burroughs’ saga of the Inner World.
If it's been awhile since you read the books and can't remember exactly what a Gilak is and where the name came from, you'll find it in the Glossary of Races and Tribes on page 132.
That, and a few other glossaries, are among the many useful features of "A Gilak's Guide...." It has statistics, book summaries, maps, articles on comics and films, and sections on such subjects as timelessness, beliefs, languages, family trees, the Hollow Earth theory itself and a bibliography of articles written by others over the years on the Inner World. There is even a Pellucidar chronology (What kind of chronology would there be for a timeless world? Read and see!).
I was honored to be asked to provide an "introduction to (the land of) Pellucidar" for the book, but was unaware of the scope of the Guide's content until I received my finished copy.
I was impressed by the range of articles -- some of several pages and some of several inches. You will find treatments on such subjects as what really happened to Jason Gridley's love, Jana -- did she accompany him to the surface or did he leave her in Pellucidar? And, if you had to locate evidence for which she did, in what E.R.B. books would you look to find that evidence? There are other tidbits, such as how to locate the two instances where E.R.B. inadvertently referred to night – a concept unknown to Pellucidarians!
The book has a color cover and nice interior illustrations by Harry Roland, including an observer’s eye-view of what it looked like when the O-220 entered Pellucidar through the polar opening. Plus, there are photos, including one of a real iron mole!
This book is a wonderful labor of love and a useful tool for the Pellucidar fan.