I have triplets plus one and they all love to read! They are hooked on Fergus Ferry (fergusferry.com) But are there any other good books out there for them to read? They are 6, 6, 6 and 9 years old all girls.
I have written a collection of 31 bedtime stories which would be perfect for your kids' age group. The book is called "A Month of Bedtime Stories: Thirty-One Tales of Wackiness and Wonder for the Retiring Child".
A couple of the stories are available for free using the "LOOK INSIDE" tab on the amazon page. You could try them out on your daughters and see if they like them. Hope they do!