I can usually live just fine with some grammar mistakes - if a story is otherwise compelling. With this book, I unfortunately only made it through the first couple of pages before I threw up my hands and gave up. The numerous run-on sentences with their missing commas or full stops were simply too exhausting to read.
Some examples:
"Hi Sarah boy am I glad to see you I've had a weird morning, how are you?"
"Great Sarah was coming round today I only see her a few times a month when her mom comes over to see mine."
"I felt Sarah behind me my mind was telling me to grab her and run but now I had frozen, my toes curling trying to grip the forest floor."
The story might or might not be good, plot-wise, but it really needs the attention of an editor or at least a good beta reader.