This is the second book I've received that had large black lettering on the edges of the pages. When I'm finished reading them will they be unpostable?

Writing on the edges is postable.

 Thank you! I knew it didn't bother me, but I wanted to err on the side of caution. :)

Unfortunately writing on a book's fore edge is okay. I once received a copy of a hardback book with "McClure" written in a Sharpie marker on the side. So, so ugly.

Personally, I hate it, but it's so rare that I don't have an RC for it.

I am about to post it in the BB or throw it away. Although I know it's postable, I wouldn't send it to anyone.

As other say - it is postable.  Personally - not bothered by it.  I am not marrying the book - just reading and I can't see what is on the edge when I have the book open.   I would be annoyed if it bled onto the text pages - but I believe that makes it non-postable.