It's remarkable you have been able to get into any retail stores, I assume there are not giant chain stores. These days people often have to self publish and sell through online marketplaces, I understand it's not hard to publish a title for Amazon Kindle.

There are people making a decent income self publishing Harry Potter like serial books, here is some self publishing info:

amarketingexpert.com

writersinthesky.com

inktreemarketing.com

ebookfriends.com

worthyofpublishing.com

Teenink

Quizilla

Inkpop

Storywrite

Booksie

Wattpad

Fictionpress

Mibba - young writes share.

Writerscafe.org pier reviews of poetry, short stories, novels, scripts, and screenplays

Youngwriterssociety.com

Writers-Network.com

As a first time seller you are doing quite good. Anyway as you have already sold 21 copies of your book, it indicates there is a demand for your Kindle ebook. And if you can promote it properly, you can make some decent money. Don't loose this opportunity.

You're doing positive things. Good Job, not bad at all.

teen selling books is good. great job (:

Hey :) I'm a teen and I wrote a children's book and It was out in 2 book stores for about 10 days. I gave 1 book store 25 copies and the other book store 25 copies. I've sold 21 copies so far. No promotion or anything like that. Is that bad?