The most appropriate option for the subject of a letter of complaint to the sales manager of a publishing house for the delivery of faulty or damaged books would be:

1. To complain about the delivery of damaged books

The chosen option, "To complain about the delivery of damaged books," accurately conveys the main purpose of the letter. Here's the reason:

- The subject clearly specifies the primary concern, which is the delivery of damaged books. This is crucial for the recipient, in this case, the sales manager, to immediately understand the nature of the complaint.

This subject succinctly informs the sales manager about the issue being raised in the letter, facilitating a quicker understanding and response to the customer's complaint. It is specific and directly addresses the problem, making it an effective and appropriate choice for a subject line in a letter of complaint.