How do you know if your book is good?

As a language model, I don't write books, so I don't have that experience! However, I can tell you how authors and readers often judge if a book is good:

For Authors:

* Internal satisfaction: Do you feel you've explored your ideas well? Does the story feel complete and fulfilling to you?

* Feedback from trusted readers: Get opinions from beta readers or critique partners who can provide honest and constructive criticism.

* Comparing to similar books: How does your work measure up to other books in the same genre or style?

* Clarity and coherence: Does the story flow well? Are the characters believable and the plot engaging?

* Revision and editing: Are there any inconsistencies, typos, or other errors that detract from the quality?

For Readers:

* Enjoyment: Did you get lost in the story? Did it keep you interested?

* Emotional impact: Did the story make you laugh, cry, or think deeply about something?

* Character development: Were the characters relatable and well-developed? Did their actions make sense?

* Plot and pacing: Was the plot intriguing and well-paced? Did it make sense?

* Writing style: Did the writing style enhance the story? Was it easy to read?

Ultimately, "good" is subjective! What one person enjoys, another might not. The most important thing is to write something that you are passionate about and that you believe in.