If the book night light fails during the warranty period, you can apply for repair by following the steps below:

Confirm the warranty terms:
First check the user manual, warranty card or electronic voucher provided with the product to confirm the warranty period and warranty terms.

Check the cause of the failure:
Confirm whether the night light failure is covered by the warranty. Usually, human damage, misuse, failure to operate according to the instructions, normal wear and tear, etc. are not covered by the warranty.

Contact the seller or manufacturer:
If the night light is within the warranty period and the failure is covered by the warranty, contact the customer service department of the seller or manufacturer where you purchased the product.
Provide your proof of purchase (such as invoice, receipt or order number) as well as the product model and description of the failure.

Describe the failure:
Clearly explain the problem with the night light to the customer service, and if possible, provide photos or videos of the failure phenomenon so that the customer service can determine the problem more quickly.

Get a repair guide:
The customer service will provide repair suggestions based on your description, which may include return to the factory for repair, on-site repair or replacement of new parts.

Ship the product:
If you need to return the product to the factory for repair, send the product to the address provided by the customer service. Please ensure that the product is well packaged to avoid additional damage during transportation.
Remember to include the purchase receipt and contact information in the package so that the manufacturer can communicate with you in time.

Track the progress of the repair:
Keep in touch with customer service to understand the progress of the repair and the expected return time.

Accept the repair results:
After receiving the repaired night light, check whether it has been repaired and sign for it after confirmation.

Save repair records:
Keep the repair records and related communication records in case you may need to inquire in the future.
Please note that the warranty policies and processes of different brands and sellers may vary. The above steps are for reference only.

Be sure to follow the specific warranty policy and customer service instructions.