Thanks to Caroline Starr Rose's great blog, I've been trying to figure out the whole number of printings thing. I'm sure I knew this at some point in my librarian/ reader/ writer career. But only when Caroline blogged about it did I decide to read up on the whole Printing vs. Edition thing.
(Thank you, Caroline, for filling my afternoon with great googling and little writing. But it was fun!)
Here's a good explanation of how to find which printing a book's in:
http://www.travelinlibrarian.info/writing/editions/#prfa
And if you're a potential book collector, this might be helpful.
http://bookriot.com/2012/11/08/the-beginners-guide-to-identifying-first-editions-part-one/
I can't resist sharing an image from that link, above.
I believe this is the copyright page from THE HELP.
Do note how many printings that book's in...
That would be #56. And it was over a year ago.
We should all be so lucky.