I don't know about all these five and four star reviews. You can adore Jane Austen, but this early work of hers is far from polished or cohesive. Of course, it was never meant to be published. It seems like it was the normal ramblings of a young teenager, writing away in her journal about whatever whim of a story came her way. Pretty much what I did at her age. I would write a story down that would last about 10 or 20 pages and then move onto my next thought.
Certainly you can see the beginnings to her novels, but it's not even close. Not that I am trying to denounce her writing - some of the bits are cute and full of soap opera drama, but they lack consistency and it can be hard to follow.
If you're a diehard Austen fan, I wouldn't shoo you away, because getting any more of Austen is a treat. Don't expect any ground-breaking literature.