Dinosaurs, the Encyclopedia

["Mortensen, Bruce" <Bruce_Mortensen@affymax.com>]

   Years ago, I bought a copy of Don Glut's  Dinosaurs, the Encyclopedia,
which was a bit pricey at the time, but seemed to be mostly worth it.
Since then, there have been two updates:

 Dinosaurs, the Encyclopedia , Supplement 1
and
 Dinosaurs, the Encyclopedia , Supplement 2

   So, the question is this - Are these three books really very different?
Are they truly supplements that carry new information not seen in each other
or in the first book?   Or are they mostly copies of each other with minimal
new material added.   How much duplication is there?   I'm wondering if they
cover enough new material each to justify buying supplement 1 and 2, or 1
instead of 2, 2 instead of 1 or just say the heck with it and wait for
supplement 3.   Would anyone care to offer their opinion?

Thanks,   Bruce