I've read all I can get my hands on so far (I'm almost 26 weeks), and my favorite is dr. Barbara Luke's book "What to Expect when you're expecting twins, triplets and more". But I'm interested to see if other moms found a book more specifically geared to natural stuff. I like Dr. William Sears' books with my last pregnancy, but I don't know that he has anything specifically for multiples...
Oh, and that book by Karen Gromada, "Mothering Multiples" is super, but it was mostly about breastfeeding. It would be a good choice too, though!