"They are two different books."

[blargblargblarg]

Could 'Sie' be used in this case?

[christian]

Not really.

[snbutler]

I'd be interested in why not too. Even if it is "es", why "es sind" rather than "es ist"? Is it a bit like the usage of "es gibt"?

[Musetta]

Really?! why not?

[surajramjee]

why not "das sind zwei unterschiedliche Bucher"? thanks.

[rmz]

Das sind means THESE ARE
Es sind means THERE/THEY ARE (Just like gibt es means there is)