An unsolicited review...
The developer has been and is very responsive to feedback and error reports and has made 3 updates in the past two weeks on his app since my purchase. He was asking $5 for it, I paid more as I feel that it's set too low for what it does, and even then I feel I got a steal for the level of the quality of the output - it's a 'no brainer' if you are an author, or someone that wants to listen to high quality eBooks and/or articles and/or blogs, etc. etc. etc., that aren't yet available as audio.
I purchased it in anticipation of when I actually produce an e-book that I want to narrate, with my own 'cloned' voice. The cloning process took all of 15 seconds of spoken audio that will capture the nuances of your voice and accent, and it sounds really good - especially if you can do voice acting with a variety of accents and styles. It does watermark your voice to protect it against unauthorized use.
While not perfect, the sound quality of what it does produce is comparable with ElevenLabs with the amount of finished product it can produce is on par with their $100 per month plan or better - saving a thousand or more per book of a 100,000 words if you hire a voice actor(s), or $100-150 for ElevenLabs = "No Brainer" and that's assuming no retakes.
Now for the negative...
Highly recommended, a dedicated video card - optimized for nVidia - I use such a card on a 12 year old desktop PC, a lower end RTX 3060 with 12GB VRAM on an ancient i7 CPU w 16 GB RAM - it's not fast, HQ encoding is roughly 2x real-time, but the quality it renders is outstanding. I would imagine the rendering speed is dependent on hardware. If the required hardware is not present, it does failback to CPU, which I understand is many times slower and I imagine frustratingly so.
The app still has a few rough edges on it and I would like to see some more features added like the ability to do direction [very limited at the moment, mostly undocumented], and different accents [missing].
Work-a-round, for the shortcomings - export different sets of paragraphs / narration / voice acting and manually segment them together where different accents/voices are needed.
The itch.io copy the installer/uninstaller is primitive; however, that should be rectified by the time it's published on Steam according to the OP in my communication with him.
To summarize...
Thank you for a wonderful product, and I do encourage you to continue to improve it, as I personally feel it can be a serious contender and potentially a disruptor to the TTS market.