KC-(quoting doesn't usually work on my blackberry!) A five star review for a book, and it's the only book reviewed isn't always bad- especially if the review is somewhat specific. Some of the ones I'm thinking of are truly just praises to the book/author and I cannot tell if the book was ever even read.
You're right, you as an author can't really control who writes a review and how they choose to write it. And it's a shame if the only reviews an author has are suspect. Hopefully as the book gets out there, more reviews will help establish the book for what it is.
You are deserving of those 5 stars though
I think you probably have enough reviews overall that it balances out "new," possibly suspect reviews with reviews from those who have several completed.