Maybe you've solved the problem meanwhile, but I'll post my solution for this issue anyway. I had the same problem (and angriness), but thanks to the few hints of King Penguin above, I was able to make it work for me.
It may help others.
1. Use a normal PC to save the mp3 files on. Rip them from a CD, or download them from a website. If it's your own website, you probably have them already stored on your PC somewhere.
2. Make sure ITunes application is installed on this PC. (see above post from king_penguin for the link)
3. Create a Playlist in ITunes (on your PC) and add mp3 files to this playlist (drag and drop to the applicable area; you'll notice)
4. Connect your Ipad to the PC, using a cable (the one you use for charging the IPAD)
5. Wait a few seconds, one minute...the icon for a connected device becomes visible (depends a bit on ITunes version where exactly)
6. Open this device, that is, your IPAD in ITunes
7. Drag and drop the files from step 3 to the Ipad area in ITunes
8. Wait a few seconds... now turn to your IPAD and open the built in Music app, et Voilà, you'll have your mp3 files
9. You can play the files OFF LINE, any time.
The whole process above does not need internet, apart from the eventual, one time, installation of ITunes on the PC and maybe the download of mp3 files.
No apps needed like GoodRead or others. Just Itunes on your PC.