Once We Were Human by Randall Farmer

 Though it appears to be a new and fresh idea, the central premise of this series, the transformation via a disease into something no longer exactly human, has been used before - the crystal singers' transition in McCaffrey's Killashandra stories comes to mind. The "monsters" need to get "juice" from a special type of transform also reminds me of the Sime/Gen novels from several decades back by Jacqueline Lichtenberg (gotta re-read those one of these days).

We start with the story of a woman who has experienced the transformation unexpectedly, which results in her killing her best friends and her own daughter, and being shackled and led to semi secret research facility where monsters like her are studied and perhaps taught to live with their new powers, if they cooperate and prove useful to the powers that be.

Then we jump to the story of a man who is living in the shadows, and has the ability to consume the dregs or waste product of the "juice" rather than subsist on the juice, itself. He is homeless, and hopeless, but then he is helped by another monster just like himself, who gives him a hand up and some good advice on how to survive in his new life.

Then I thought, "I have more interesting things to read" and I have no idea how it all turns out. Though there are plenty of sequels, I find no motivation to follow up here.