It starts out in the year 1806, when Wentworth (at the time a Commander, not Captain yet) and Anne meet for the first time. Persuasion, by Austen, begins in the year 1814 ... I believe. As Grange writes the first part of the book (almost half), she is going by her own imagination. So, really, if anyone were to write a book about what they thought Wentworth was like based on imagination you would come up with, perhaps, a different description from each person. That said, I pictured him different from what Grange did.
Over all, the book was well written. After the first part of the book (the 1806 part) when you're in the year 1814, the events closely follow Persuasion. It was fun to see how Grange thought Wentworth would respond. In some parts I thought the same as Grange as to how Wentworth was thinking and sometimes I imagined Wentwoth responding differently. But since Austen did not write this book, we really don't know how she originally pictured Wentworth.
The book was interesting and rather fun. Would I read it again? Maybe not, but that's just my personal preference. I thought it was a good book. There was nothing bad in Grange's writing. It just isn't the kind of book that really grabs my attention to read over and over.
So, all that said. I'll leave it up to you if you want to read it. I guess I would recommend it, just for fun.