Except apparently this will no longer work for heavier books, because I did not know that according to "heightened security measures", if you're mailing something that's more than sixteen ounces, you are required to hand it to a retail clerk at a Post Office. In other words, no dropping items into the mailbox anymore.
So today a package of mine with a single book in it was actually returned to me, with a note attached explaining all this. Now I have to take this package to the post office tomorrow and hand it to the clerk, whereupon we will have the following conversation:
CLERK: Is there anything liquid or perishable in here, sir?
ME: No. It's a book.
CLERK: Any insurance of verification of delivery?
ME: No, thank you.
CLERK: OK. [puts package onto the pile of outgoing stuff] Need any stamps?
ME: Got any of those Star Wars stamps?
CLERK: No, but we have the Great Moments in Frozen Food series.
ME: OK, fine.
CLERK: Have a nice day.
That's all that will happen. Believe me, I've mailed enough books through the years that I know whereof I speak. So how is this in any way to help with "security"? It's not like the mail clerks are going to assess my package for its potential bad-stuff-containing possibilities right then and there; surely the package will be scanned at some point in the mail-handling process, but as all the mail ends up at the same place eventually before being redistributed again, who cares? How will any of this prevent someone from hollowing out the pages of a book, Andy Dufresne-style, and mailing nefarious items that way?
This is a stupid, stupid rule.