Disclosure: I know the author. I in fact rather like her, she's a nice person.
That out of the way, here's my take on Finding Gaia: It's a really good book. I thoroughly enjoyed reading it, the premise is smart, the supernatural elements work well within the context of the story, and the characters, importantly, are very well put together.
The characters are really the best part of this book, and boy do they shine: Jason is broody but not annoyingly so, and for good reasons. Trish is sharp-tongued and witty, but not heartless. Don is a huge nerd, but also really wise in a lot of ways. Anna... Anna is really the best characterization of them all. She's been hurt, and the scars show, but she is a survivor. She heals, even when the pain seems insurmountable. I could not help but love her.
This being, at its heart, a romance, I would be remiss to not mention that the relationship between Jason and Anna is built very deftly. No insta-love here, they need time to even be okay with their feelings about one another. It's quite smartly done, and rings very true throughout.
I could perhaps have wished that the story had a different pacing, but I'm honestly not sure if that isn't just because I'm not familiar with the structure of a romance - I don't read a lot of them. Certainly, the story is well told and entertaining, and occasionally nail-biting. And since this is literally my only niggle, this book ends up coming very highly recommended indeed.