You know the idea...
The book is a hardback reference catalogue that might make it a little easier to find the exact "blank slate" you're looking for. More than 1,000 images are labelled with codes that correspond to the TIFF files on the included DVD.
All images are available on white and on black backgrounds, except for the few in the sadly lacking "environment" section — it's a shame there isn't a wider variety here.
I've built a decent library of these images, but this is a nice alternative to signing up to a stock photography website, and I'm sure I'll make use of it at some point soon.