Insurance companies must have a substantial amount of capital to cover potential claims from policyholders. This is known as the insurer's book value or total amount of insurance. It represents the financial strength of the company and its ability to fulfill its obligations to policyholders. It is an important factor for investors to consider when evaluating the financial stability of an insurer. Without sufficient book value, an insurance company may not be able to pay out claims, leaving policyholders vulnerable. So, it's crucial for insurers to maintain a healthy book value to ensure the security of their policyholders.