I recently sent my largest value of books into a new presser/cleaner. And I wanted to see what a majority of people did when shipping. This post will cover what some of the more seasoned collectors have done to protect their books.
More than likely you'll be using USPS Priority mail to ship your books. Each time you use them $50 of insurance is automatically included no matter what size Priority package you get. A great tip when determining how much to set the price of insurance on your package is to insure the value it would cost to replace the books. I was originally going to just set the amount for the value of the books. However I upped it because it didn't take into the account taxes, fees and shipping of buying back lost/missing books. And sometimes a particular book, especially if in high demand or rare, will cost much more than you paid in order to get another copy.
Some collectors also use a third party insurance company in order to add an additional layer of protection. I myself use one that covers my books in transit as well as protection at home. Bear in mind that insurance requires a lot of work on your part as well as a lot of patience. Some people claim it can be 90 days+ before getting a response about a claim from the USPS. Times and amount of work will vary with each third party insurance company. Also I've heard that the USPS if they do pay out, will keep the books.
Now you're probably wondering what I was submitting throughout reading this post. My submission was 5 books, 3 copies of Amazing Spider-Man #252, Silver Surfer #44 CGC 9.2 and Secret Wars #8 CGC 9.6. I originally was going to do insure it all for $500 but that definitely would not be enough for me to buy the books back with taxes, shipping and fees included on those books. Next time you send something in for grading or cleaning/pressing be sure to add a little more to the insurance amount so you're covered.