BUT. What you have, I'm afraid, is not yet a book. It's a draft. Even if you've already slaved over it and edited it and rewritten it til you've dripped blood on the keyboard (ew, please don't do that), in order to make it really sparkle, to make it stand every chance of getting picked up by an agent and publisher, you're going to need fresh eyes on it. And fresh eyes means knowledgeable critique partners.
It isn't enough just to have a couple of friends who don't even read in your genre cast an eye over it. They probably won't know what to pinpoint, and they're your *friends* so they'll be scared to say anything that isn't YAY LOVED IT for fear of damaging your friendship. You want feedback, HONEST feedback, from other writers. Don't worry if you don't know any other writers. Almost nobody does when they start out. So where do you find them?
Twitter: Are you on Twitter? You should be. The writing community there is incredibly friendly, supportive and helpful, especially the kidlit/YA crowd. If you're brand new and don't know who to follow, try following some of your favourite authors or bloggers and see who *they* follow or are followed by, and just chat to people. Once you've made some pals, you can tweet that you're looking for a crit partner for your amazing new middle-grade zombie-dragon story, and see if you get any takers.
How About We CP: An excellent Tumblr with regular updates from writers of all genres and categories who are looking to hook up with new CPs.
Critique Partner Love Connection: Set up by bestselling YA author Maggie Stiefvater. A great place to find CPs, especially if you write YA.
CPSeek: What it says on the tin. A website set up specifically for writers seeking critique partners.
The Blueboards: The official forums of SCBWI, the Society of Children's Book Writers and Illustrators. BUT you don't need to be a member to read and post there. You do need to register and post at least fifty times in order to gain access to certain parts of the boards, but if you write kidlit or YA this place is not just somewhere to find crit partners, but also an absolute gold mine of information on every aspect of writing and publishing for children and teens. It's also an incredibly friendly and supportive place. I really, really recommend it.
Then if the chapter-swappage goes well - congrats, you've just found yourself a critique partner! Now all those lazy bits of writing, inadvertent plot holes, and info-dumps will (hopefully) disappear with their help. Also, don't stop at just one. If you can find two or three, then do. That way you'll have enough feedback to know if your main character really *is* hopelessly unlikeable, or if it's just one person's opinion.
ADDED BONUS: Critiquing other people's work - as opposed to just having your work beta read - will help to make you a better writer. And if you're really lucky, your CPs will become good friends too. Win/win!
PS If you have any other tips on where to find CPs or what to do with 'em once you've got 'em, feel free to chime in in the comments :)