Ask yourself these questions whenever you're starting a new book/story/poem, whatever;
What is your message?
If you were a reader of this book, what would interpret from the book?
How do you want the readers to feel while reading it?
How can you make it more gripping?
Would you pick up this book if you saw it a store?
If not, how could you make it more interesting for you to buy it?
Is there a strong plot? Have you spotted any plot holes?
Have you made your characters realistic?
Even if they are super heroes from magical planets or whatever,
have you made them somewhat relatable to the reader?
I'll add more questions later xoxo