My baby has showing signs that she like books from when she was 4 months old. In the picture, I think she was already 5 months though. During these times, she would chew on everything that she could get her hands on, except books. So we started exposing her early to books. Here is one of our reading sessions. I would read the contents aloud and point to the items in the book.
We got this set of 4 Early Learning Board Books by Brainy Baby from a friend during our baby's baptism when she was 2 months old. Two months later, we were already using the book. I think the baby likes the many items and colors in the book. She is very enthusiastic when we read. I also like the varied topics--123's, shapes and colors, ABCs, and animals--with one book dedicated or each topic. I think the entire set costs around $6, but it is really a good investment in order to stimulate baby's brains early.
The pages of the book has white background so that the items described stand out. The surface is shiny so it doesn't get dirty easily, unless of course it is soaked for a long time. A little grime could just be easily wiped off. In our case, reading time is not mixed with eating time, so there is no problem with staining. The edges of the book are rounded so they will not hurt the baby.
I would recommend this book to parents of babies from 4 months up to 2 years old probably.