I have over 800 books there
So it took a while for me to check. (This is only books purchased at Harlequin.com, not all of their books bought elsewhere).
Thankfully I have a "source" column in my Calibre Warehouse Library where I list where my books were bought/free from. So I just created a catalogue with title and author only, copied it to Word, and printed it to cross off the titles as I went. I left them in order by date, but would have been better off sorting them by title or author as the most time consuming part was going through the books during that sale in 2011. So very many books bought on Christmas and Boxing Day.
I 100% agree they should have given more notice.
At least they finally sent out an email about it. Which is good because not everybody checks their store every month to have seen the notice. I also think it's nice that they have included the info in all of the receipts for the books I redeemed this week. But I am sure they have customers who still do not know and will be upset after the fact.