What are "remainder marks" and do these marks make a book unpostable here if we get hold of such a book? Thanks.

The only thing I found about this was here: http://reviews.ebay.com/What-exactly-is-a-Remainder-Mark_W0QQugidZ10000000001625850 There's even a nifty picture.

"Remainder marks are generally simple; they often look like random dots or streaks from a black or colored magic marker. Remainder marks vary from the tactful, to the gaudy, to the look of being accidental.

The purpose of the remainder mark is when a store does not sell a book they mark the bottom or top edges.  The remainder mark is put onto the book and returned to the publisher to make room for new inventory.  Then the publisher will re-sell them for a discount rate.  That is why when you see a book with a remainder mark it is usually for a discounted price.  It's a way of tracking the book once it leaves the store.  From a collectors stand point a book that is Remainder marked is not worth as much as a copy that is not.  The Remainder mark that is on top edge of a book is worse from the stand point that you can see the mark when shelved. "  

I have received a book with a remainder mark on it and thought nothing of it. I would think it would be postable, but someone else may have more information. I see it as being no different than a sticker and I don't think it counts as writing on a page, because it's not technically on the "page" but on the top/bottom/side of the book.

Books with remainder marks are postable. Remainder marks are usually a line or a dot made with a permanent marker across the bottom edge of the pages of a book to indicate the book was not sold at full price, but as a clearance or deeply discounted item. Since the remainder mark does not obliterate the text of the book, the book is still postable. (It's just like other markings on the outside of a book or inside the cover.)

What about a mark through the barcode?

That is fine too, Ricki. Some libraries and used book stores do that.

Marker, stickers, and other writing on the outside of the book is generally OK unless there is so much that it makes the book not "in good condition". Yes, that is a subjective opinion.

Writing is also OK on non-text pages. Writing on text pages may provisionally be OK ... you are required to notify the requestor of such and get permission before the book is mailed to them.

Dirt, stains, water, other liquids anywhere in the book make a book unpostable. Sometimes dirt can be removed from page edges carefully with sandpaper.