Two distinct single-post templates?

I’m doing work for a client who has used WordPress in a non-traditional way. His “posts” are actually listings for books he’s selling, and if you click one, you get a details page about the book. Needless to say, the details page uses the single.php template.

But now he also wants a Blog section, and that too will need to use single.php. So can I create a separate single-post template for the Blog? I know you can do this with categories by creating “category-1.php” and so on.

Thanks!