I'm Unsure

So the reason I titled this as "I'm Unsure" is because I'm very much in two minds about how I feel. The book is hinging everything on the tension of "this man is missing because of a sinister reason and not because he's just not into the girl" and because it's a book and so on, the reader can generally assume that this is the case. However, based solely on the first impression, I do not know enough about the characters to assume that something is amiss and that Eddie wouldn't be the type to simply leave. Sarah is a tiny bit more fleshed out but I still don't know enough about why she's so hinged on Eddie besides from "he felt like he was the one". So I'm a little frustrated. Because I know there is probably going to be a good twist and intrigue around this story but I currently don't feel like that from the story.
However, the car ride and all associated descriptions and character interactions feel very real. I have a soft spot for Rudi especially.
I'd like to read more to see if something more grabs me but at the moment, I'm in two minds.