I have a feeling everyone will think I'm crazy but, I have a system that works for me and is pretty quick. I usually set up folders and do the pic of the purchase page while the book is being downloaded.
I have my books in author folders inside 1 of 2 main folders for books. The 1st for DRM'd books and the 2nd is for DRM free books.
Inside the author folder I have separate folders for each book. The book folder title has the information as the folder name. R is what I use to show that I have read it, $ means I purchased it, and then the month and year.
- A bk1 of Lady by John Doe R smashwords free 1-2010
B bk 2 of Lady by John Doe R smashwords $ 1-2010
C by John Doe smashwords $ 2-2010
Inside each book folder, I keep a pic of the book purchase page. Which also has the book blurb to refresh my memory. I also keep multiple formats of the book in each folder.
Then, I change the book folder icon to reflect what genre it is.
Humour
Mystery
Sci-Fi
My DRM'd books (which means the backup copies of Sony Reader and ADE books here) has this main folder icon.
OK, I know most will think it's a lot of work or crazy, but it is fast and works for me.