Is it obligatory to inform the owner of a book immediately if its cover is damaged, or if it is written in, or if it is lent to another person without his permission?

If the borrowed item is damaged or depreciated in the borrower's possession due to authorized use, there is no liability on the borrower. However, if it is damaged due to unauthorized use, the borrower is liable.

If the damage to the book cover is due to normal use during reading, the borrower is not liable and is not required to inform the lender. However, if the damage is due to negligence, the borrower is liable for the depreciation.

Writing in a borrowed book is not permissible without the lender's permission. Otherwise, the borrower must inform the lender to seek forgiveness or compensation.

As for the borrower lending the borrowed item to someone else, the preponderant opinion is that it is not permissible without the lender's permission. If this occurs, the borrower must inform the lender and seek his forgiveness, because by doing so, the lender is entitled to the customary rental fee.