Okay, so the Kindle Fire does not have a text-to-speech function despite this e-mail, which I got from Amazon Customer Support:
As a new Kindle Fire owner, I get a month of free Amazon Prime, which means not only free shipping on actual hold-in-your-hand books, and even deeper discounts than usual, but lots, and I do mean LOTS, of streaming video, that I can watch whenever I want, including every X-Files episode, several seasons of The Twilight Zone, most of Star Trek, and lots of Mystery Science Theater 3000 (do we sense the drift of my TV watching taste?). I can also watch many many movies for free, and many others for less than it would cost to rent them from a brick and mortar store. Though I'd never been tempted by Amazon Prime before this, I have a feeling that I will shell out the $79 per year from now on. Smooth move, Amazon.
So, I can watch TV and movies as I exercise, which helps to make up for not having TTS. But, I can also listen to books as well.
Back when my Zune was fully functional and Microsoft thought it was going to push the iPod out of the #1 position, I used to subscribe to podcasts and the RSS feeds would transfer directly to the Zune. I listened to many books via Librivox that way. Their vast library of recorded books (all done by volunteers, and all in the public domain) kept me happy for a long time as I sweated away. And they're keeping me happy again.
So, just in case you have a Fire, and you don't know know how to use it to listen to these audio books, here's what I did (and if there is a way to subscribe to podcasts directly, I haven't found one- if such there be, please let me know).
#1. Go to Librivox and select the book you want to hear. This morning, I selected Book #3 in the John Carter of Mars series, The Warlord of Mars.
#3. In Librivox, click on the book listing. Below the RSS information, will be a listing of the MP3 files of the book, arranged by chapter.
#4. I have no idea what an ogg vorbis file is, but it doesn't matter because we don't need that link. I also don't know what the difference is between the two MP3 file types- I chose the 64kbps for my downloads, just because. Anyway, click on the Chapter 1 64kbps link, and this window will open:
#6. Find the folder with the book title, and save the chapter file there.
#7. Repeat with all of the chapter files of the book.
#8. If you cannot connect your Kindle Fire to your computer, go to Step #10 If you can connect your Kindle Fire to your computer for a direct transfer (sideload) of the book, do so now. When the Kindle shows up on your Computer as a device, click to open it.
#9. Find the file folder with the saved MP3 chapters on your computer, drag and drop the whole book folder (you don't have to do the chapters individually) to the Music folder of your Kindle. The transfer will be made. To listen to your book, just open the Music App, find the Book Title (the Kindle will treat it like a CD), open it, choose the chapter you want to listen to (the Kindle treats the chapter files as individual songs), and listen.
#10. If you cannot connect your Kindle Fire to your computer for direct transfers, then go to your Amazon Account, and click on Manage Your Kindle, and then under Other Digital Content, click on Manage your MP3 files. Follow the instructions for uploading the book chapter files to the Cloud (you might have to download a Cloud app first). This takes awhile (30 minutes the first time I did it, before I figured out how to make a direct transfer).
#11. Open the Music App on your Fire, and find the files stored on the Cloud, and download them to your device. Open the chapter you want to listen to, and enjoy!