Nope, not according to the post office.

I mail a lot of books and would not put any but the thinnest in a manila envelope. I use poly mailers that I buy in bulk on ebay. (they are cheaper than Tyvek).

You can get $.19 Delivery Confirmation with Media Mail if you print postage from Paypal. Unfortunately you can not print MM postage on the USPS website.

You can use the Tyvek mailers or padded envelopes and still send Media Mail. . . Doesn't have to be just a manila envelope

One of the reasons that "Media" and "Book" rates are slower is that they go through the bulk mail center. Bulk mail consists of parcels, advertising mail, etc. No first class, priority, periodicals, or Express Mail, goes to the bulk mail center. So, if you do send a book in a manilla envelope, it will be processed with all the heavier packages in the bulk mail center. All processing is done with machinery. I would never recommend using a manilla envelope for a book. At least use a padded mailer or a cushioned mailer...