I'm about to become a mom for the 2nd time, and thought that it might be nice to include a chapter in your book about this topic. Maybe list things that you don't need because you still have them from baby #1, as well as things that multi-baby moms find incredibly useful for more than 1 baby (like 2 babies, or a new baby and a toddler, whatever the situation).
Just an idea!
~Lenore