Any idea what the differences would be? Do both basically just focus on north american beasties? Like vol 1 is A-M and vol 2 will be N-Z?
Note: If these two volumes do well, future volumes will include spirits, ghosts and entities, another on dragons, other volumes on creatures in other parts of Rifts Earth, and so on.
I'm really interested in the first, though I do wonder how much of it might be reprints from Dark Conversions + Madhaven... similarly "Dragons" sounds like it might also be reprints of the various variant species from D+G/RUE/England/Japan/Psyscape/SpiritWest/Canada/Lemuria so am a bit hesitant about that too...
If the 'creatures in other parts' would have a lot of new content not present in earlier world books that would be great. In the very least I hope it's all new art if it is a reprinted species, with new notes.