i have a paperback with the upper corner cut off. i remember reading what that meant but now i cant find it. I also noticed a stamp across the top of the book that says " not tradable"  it is like someone stamped it on the papers edges.  is this book still postable?  it appears to be in really good shape besides these 2 'problems'

Sounds like it was on "clearance" at a Used bookstore...mine cuts the corner, but they dont' also stamp it.  It means you cannot trade it back to them for credit.

Cut corners up to 1" are postable, yes, and the stamp would be similar to a library stamp, which is allowed.

Some used book stores do this. As long as the piece that has been removed from the cover is less than 1 square inch, it's fine. A stamp or name written on the page edges is postable, even if it says "not tradable."

Here'ssome info from the help doc about the cover:

Cover:

• Must both be present (front and back)
  • note that a paperback missing its front cover is  usually an illegal, unsold copy
  • "cover" does not = dust jacket.  Hardcovers do not need to include their dust jackets to be swapped here.
• Cover not water damaged (there may be no water damage to any part of the book)
• Cover not torn or chewed/gnawed
  • some used book stores cut out a small part of the cover; if the amount missing is less than 1 square inch, this is OKAY
  • a small rip (less than 1 inch) in the cover is OKAY
  • yes, that does say "chewed/gnawed" above.  That means no pet-chewed (or human-chewed) books.

I used to live near a UBS that stamped clovers on the page edges and flyleaf.

I used to live near a UBS that stamped clovers on the page edges and flyleaf.

Mine used a Minnie Mouse stamp for the ones that were final sale.

Thanks to everyone who answered, you guys really did help. i appreciate it.