I just posted a book and the binding already listed for it was "perfect paperback."  I've never seen that before, and in fact mine isn't perfect technically since it has an allowable name written on the first inside page.  Just looked on the 'Posting a book without an ISBN' page and there is no default binding with 'perfect' in it.

Perfect binding is a type of book binding. It does not refer to the condition of the book. Here is something from a book binding Wiki for you.

Perfect binding is often used, and gives a result similar to paperback books. National Geographic is perhaps the best known of this type. Paperback or soft cover books are also normally bound using perfect binding. They usually consist of various sections with a cover made from heavier paper, glued together at the spine with a strong flexible glue. The sections are rough-cut in the back to make them absorb the hot glue. The other three sides are then face trimmed. This is what allows the magazine or paperback book to be opened. Mass market paperbacks (pulp paperbacks) are small (16mo size), cheaply made and often fall apart after much handling or several years. Trade paperbacks are more sturdily made, usually larger, and more expensive.

Sara, thanks for the info.  I've been here for 2 years and have never seen this kind of binding posted. Guess this is my new thing learned for the day!

Thanks Sara for the info. That was very interesting. That sure explains why mmp's don't last as long as the other bindings, especially trade paperbacks. Also, noticing that more pp's are taller than others now. I guess so that they can get more text on a page and not be trade covers?

That was a great lesson for all of us Sara!  Thanks.

Thanks Sara and Cindy!  I learned something new!