JSpeak is a FOSS (Free Open Source) Application I created for Linux, the only of it's kind.
It's full of features. It's primary feature is it's ability to read text copied to the clipboard. It also can use Mbrola voices. It expands and retracts to a smaller graphical user interface that is perfect for hovering over your ebooks, websites, etc. while reading from them. It's located on Github at
https://github.com/BullShark/JSpeak under the GPLv3 and above, free of charge.
The full instructions on getting it running and how to use it are there on that github link. There is also a wiki there on Github.
Please check it out. I would really appreciate it as well as any feedback and/or support through donations. If you like this software, please make a donation to help further development here on my blog. Thank you.
A few screenshots running under Fedora with Gnome3