Requested book arrived with a one-page computer-printed insert directing me to a website for buying products that will help me lose weight.

Of course that's not allowed by the Post Office, for Media Mail.

Is it allowed by PBS for books mailed First Class?

I don't recall seeing any instructions or directions to members, about what they should or should not send with books.

PBS is really strict about no ads included.  No politics.  No religion.  No ads.  Please report this.  PBS will send the member a warning. 

Part of this is the media mail rules.  Part is that our membership is national and very diverse.

(Oh.  To report it, use the Feedback option on the bottom of the page.  Under Company, then Contact Us, then Send Us Feedback.)

May I include anything with my book?

Generally: No.

Media mail regulations are very strict: only media (books, CDs, DVDs, VHS tapes) and an invoice (page 2 of the PBS wrapper qualifies as an invoice) are allowed to be sent using Media Mail rate.  No advertising, commercial solicitation, political materials, religious tracts, non-Media items, letters, cards are allowed.

• Media Mail is subject to postal inspection
• If your package is found to be in violation of Media Mail regulations:
  • Your package may be returned to you
  • Your package may be delivered to the requestor postage-due
  • Your package may be destroyed.

What is Allowed in a package sent using Media Mail rate:

• Media, as described above
• A note with a simple accompanying message,
  • such as "Happy Birthday!" or "Hope you enjoy it!"
• An invoice or notification of the shipment
  • The second page of the PBS Wrapper falls into this category.
  • The USPS eligibility guidelines for enclosures and attachments for Media Mail say (we have edited these for relevance; the full regulations are at http://pe.usps.com/text/dmm300/173.htm#wp1060522)

  • 4.0 Attachments and Enclosures

    4.2  Enclosures in Books  (bound into the books)

  • a. Either one envelope or one addressed postcard may be bound into the pages of a book. If also serving as an order form, the envelope or card may be in addition to the order form permitted by 4.2b..

    b. One order form may be bound into the pages of a book. If also serving as an envelope or postcard, the order form may be in addition to the envelope or card permitted by 4.2a..

    c. Announcements of books may appear as book pages. These announcements must be incidental and exclusively devoted to books, without extraneous advertising of book-related or other materials or services. Announcements may fully describe the conditions and methods of ordering books and may contain ordering instructions for use with a separate order form. Up to three of these announcements may contain as part of their format a single order form, which may also serve as a postcard. The order forms permitted with these announcements are in addition to, and not in place of, order forms that may be enclosed under 4.2a. or 4.2b..

    4.3 Written Enclosures

  • Markings that have the character of personal correspondence require, with certain exceptions, additional postage at the First-Class Mail prices. The following written additions and enclosures do not require additional First-Class Mail postage:

    a. The sender's and the addressee's names, occupations, and addresses, preceded by "From" or "To," and directions for handling. (page 2 of the PBS Wrapper qualifies here)

    b. Marks, numbers, names, or letters describing the contents. (page 2 of the PBS Wrapper qualifies here)

    c. Words or phrases such as "Do Not Open Until Christmas" and "Happy Birthday, Mother." 

    d. Instructions and directions for the use of the item mailed. (page 2 of the PBS Wrapper qualifies here)

    4.4 Invoice (page 2 of the PBS Wrapper qualifies here)

    An invoice, whether it also serves as a bill, may be placed either inside a Media Mail piece or in an envelope marked "Invoice Enclosed" and attached to the outside of the piece if the invoice relates solely to the matter with which it is mailed. The invoice may show this information:

    a. Names and addresses of the sender and addressee.

    b. Names and quantities of the articles enclosed, descriptions of each (e.g., price, tax, style, stock number, size, and quality, and, if defective, nature of defects).

    c. Order or file number, date of order, date and manner of shipment, shipping weight, postage paid, and initials or name of packer or checker.

Including anything but the ALLOWED materials above in your package is a serious infraction of not only PBS rules, but also Federal law. Including inappropriate materials with your books will jeopardize your membership at PBS.

What Emily said   The short answer is NO, PBS members should not be including ads, solicitations, or religious tracts with books.   Doing so violates MM regulations and PBS membership rules.

Does it seem like it was meant as a solicitation? Sometimes I just use a random piece of paper around me as a bookmark.

I'd sent a generic warning to the member to that they should double check that nothing is forgotten in the book as if it was sent media mail, the item that had been left in the book could have been classified as advertising under Media Mail and charged for. 

I would err on the side of it being a previous bookmark and not see it as a big deal.  I often use those Value-pack coupons (a ton of coupons that come in one mailing) as bookmarks and could very easily accidentally leave one in when mailing.  

I am another who uses unwanted ads or random scraps for a bookmark. I do it so often that I am in the habit of giving my books a good shake before I mail.  So possibly just a mistake?