Got two questions about the conditions of postable books. 

I have one book that I want to post that is in excellent condition. However, it is a book given to me by a friend and posted on the corner of the cover is a sticker that says 'Property of so-and-so'. I tried to peel it off but only got a corner and I always fear taking liquid cleaner to the book to get the sticker off. So with the sticker on, is it postable?

And the other one is a book I recently received in the mail and am trying to figure out if it is a RWAP or not. It has some kind of brown smudge/stain on the outside edges of the book, not a pen marking like a former library book but something that definitely looks like a stain/smudge of something. There is nothing on the inside of the pages themself, it's only on the outside pages. I can't recall if marks like that get a pass because they're on the edges of the pages and not on the inside of the book.

Thank you for your help!

Yes, stickers are postable.

Dirt or stains are always unpostable. Marks with writing implements on the outside edge of pages are generally postable.

However, if the dirt or stains can be removed, you can make the book postable again. Sandpaper can often be used to clean page edges. And, non-text pages can be completely removed from the book.

So, if you have a stain, on, say, one of the "book review" pages that is not a text page of the book ... the stain makes it unpostable, but removing the page would make the book postable again.

I often swipe the covers of my books with a baby wipe and it removes the surface dirt.  Not enough moisture to do any type of damage, but the stains (and oftentimes marks) come off.  

What they said

Stickers - just leave them, there is no rule against stickers on the book and you risk damaging the book.

Staining, soiling, and liquid damage get no pass anywhere or too any degree. The site rules say none of that is allowed at all. Because some page edge soiling or stains that haven't seeping into the pages can be removed with sandpaper you can possibly return the book to being postable by removing the problem, but you cannot post a book with the stain/soiling still on it.