|First book + bad review = PAIN|
Reality check new writer: anyone can write those reviews and despite the claims that editors check them, there is not all that much that Amazon and their ilk can do to guarantee the veracity of the reviews received. They have a program that compares the writing styles of reviewers, but this largely catches authors who are giving themselves fake praise to pump up their ratings ... or are giving a competitor devastatingly bad reviews to electronically kneecap an opponent (shame on you for sinking so low). They can't do much more because they have a huge volume of books and couldn't possibly check all that comes in.
Even if the review is made by someone real, it could be someone angry that he or she wasn't included in your book and is writing in spite (happens in niche market books all the time). Or, as happened with one of my books on a form of antique ceramics, the person writing is a complete novice and knows nothing about what he or she is talking about. In my case, the admitted novice was angry that my book on a Victorian ceramic form didn't include every form or pattern and rated my book badly. What she apparently didn't know is that Victorian ceramics have 101 pieces in a table set and that particular type had over 1500 known patterns. Had I created such a tome it would have been so unwieldy no one could have ever lifted it or afforded it. Nor is my life long enough to write such a volume. I was not devastated by this review because I had been writing for a long time by the time this one showed up and I saw it for what it was. You, new author, don't have that perspective.
Save yourself the heartache and avoid checking the status of your book on the online sites. The reviews aren't written by professionals there and the folks who write definitely don't have your best interest at heart. Many of them have no idea what it takes to write a book in the first place and a great many of them will speak from ignorance (meaning the high praise from some will be worth just as little as the bile from others). Protect yourself, new author, and turn to your own marketing of your new baby. Enjoy this first published book. You'll never feel quite the same about a published book again (provided you keep writing ... which you won't if you take bad reviews to heart).
If somebody else is handling your marketing, then go start your next book! What are you hanging around here for?!