Although a lot of people -- including many sci-fi and fantasy readers -- may not recognize the name off-hand, Burroughs is probably best known for his Tarzan series. That's how I knew him -- I'd actually never heard of the Barsoom (Mars) series, but since I'm a bit of an amateur book collector, I knew of the old Tarzan books. Believe it or not, old children's series books are highly collectible.
Anyway, I downloaded A Princess of Mars to read on my Nook (you can get it for free from Project Gutenberg) and read it. Despite the old-fashioned storytelling style (it was published in 1912, so it reads rather like one of H.G. Wells books, with lots of detail and descriptions), I really enjoyed the story. It's fairly short -- about 160 pages on the Nook -- and I'm even more excited about the movie, now that I know more what the book is about.
The Barsoom series has 11 books in it, although only the first 5 are part of the public domain (which means they are available on Project Gutenberg). I'm planning on reading at least a couple more. I hope, if the first movie does well, they'll make the next one too, as -- judging by how the first book ends -- it seems like it's a fairly important sequel!
I guess this is a lesson: Never discount the older books in a genre, as they might be better than you expect!