i started 'reading' books with my bb when she was two months old. now she is 11 months old, she can take her beloved books, read the pictures and enjoy herself.
board books are much recommended. they are hard enough. (of course, bb like 'eating' the books. it is much better for us to keep an eye on them when they read)
Sooner the better, whether they understand or not is never important. You are just playing as a role model on reading books and speaking out. Babies will learn from your body language.