Younger babies don't have a long attention span and may not quite get the concept of reading stories to them. However, they love the sound of your voice, so starting to read to them is never too early.
Get a couple of short books with little text and big colorful pictures. Read the book to baby before bedtime when she is relaxed and sleepy. As you read, show her the pictures on the pages so she can start relating your words to the book. Of course at first she won't know that you are reading a story to her, but if you keep doing this as she grows she will become accustomed to it and slowly start to correlate your reading to the story in the book.
This will also ensure that she will grow to like books and reading, something very important for young children in order for them to develop and learn vocabulary.