This is easy to fix — nothing is wrong with your book.
Why this happens
In most templates, the Table of Contents (ToC) and Index are automatically created using the chapter titles you enter.
Some chapter title pages are designed to display in ALL CAPS (for example: BREAKFAST or MAIN DISHES). Even if you type the title using mixed or lowercase letters, the page itself may automatically display it in uppercase.
However, the Table of Contents may use a different formatting style — such as “Breakfast” instead of “BREAKFAST.”
If your chapter title was typed in mixed or incorrect capitalization (for example: bReakfast), the ToC may display it exactly as you entered it.
How to fix it
Go back to the chapter title page.
Retype the title using the exact capitalization you want to appear in the Table of Contents.
For example: Breakfast
Not: breakfast or bReAkFaSt
Save your changes.
The Table of Contents will update automatically.
How to check if it’s correct
After retyping the chapter title, look at how it appears in the menu on the left side of your screen.
If it appears the way you want it to look in the Table of Contents, you’re all set.
Good to know
The ALL CAPS styling you see on the chapter page may be part of the template design.
The Table of Contents formatting depends on how the template is designed and how the title was typed.
Preview your book to confirm everything looks the way you expect.