I just posted a bunch of kids' books in 2 series and several of them have "?" or "other"  or "unknown binding" listed when they are definitely paperback books like the others in the series.  I "tagged" them as "Paperback: NOT UNKNOWN" since that was an option under the commonly used tags, but I just don't understand why so many books would be listed that way.  Any thoughts from you long time members?

Often times that's just the way the listing is when it comes into the PBS database. The information here is compiled from other databases. Unless someone does the research on a book and submits an edit, the information will stay the way we get it. With the volume of books here, there's no way for the edit team to get them all.

Unless you have researched and confirmed that paperback is the only binding that ISBN comes in, I wouldn't tag the book indicating that is the binding. A listing with unknown could get more than one binding posted to it if they carry the same ISBN and someone requesting the book may think they are getting a paperback because of the Tag, and end up some other binding.