Well...for one, Tolkien (being a linguist and a philologist) developed a number of different languages for Middle-earth. For one of the Elven languages, you can actually become fluent. You can become conversational in a couple of his other languages, too.
He also developed a huge mythology, too, which was published posthumously in The Silmarillion and a bunch of other books. They go all the way back to the creation of the world, the demigods that shaped it, and the rise of evil through Morgoth and his servants, Sauron being one of them.
The mythology can be a bit dry at times, but it is deeper and more thorough than just about anything out there. It's crazy.
A million words? That's...wow. What's your favorite?
Teddy! Incredible man. If you've never read The River of Doubt, it tells the story of when he lost the race for the Presidency under the Bull Moose flag and decided to cheer himself up by charting a section of the Amazon that had killed every other exploration team before him. He wasn't just the ultimate manly man, he was also incredibly considerate and wouldn't sit on the chair that they brought for him, instead preferring to sit on the ground if the grunt laborers in the party didn't get a chair as well.
If you like science, you have to check out Phantoms in the Brain - it was the book that first got me into neuroscience. The author Vilyanur Ramachandran, is the greatest storyteller to come out of the field since Oliver Sacks. It's not physics, but there is so much to learn! Have you tried any of Hawking's stuff yet?
Normally this is the part of the post where the thought processes start to slow down and the writing winds up, but that's not really happening...just one more paragraph...one more book to bring up...
Alright, one last question: what's interesting about To Touch a Wild Dolphin? That stands out on your list. I can certainly see why the topic is interesting, though. The episode "Hello" of Radiolab talks about the attempts to decipher dolphin communication and build a human-to-dolphin translator, and it's pretty amazing.