I talked a lot to my babies from the time they were small. As soon as they were cooing and babbling and able to have shoes and socks put on, we'd play This Little Piggie with their toes, do Itsy Bitsy Spider up their arms, and we'd say "Toes", and "Foot", and "Sock", and "Shoe" as we dressed them.
I had mostly early talkers... But then, the house was pretty full of naturally verbose people once the first one or two got going.
I did not READ to them at that age, but I'd point to things in the book and say the names.
The words babies learn first are the ones that are repeated to them, and that are either necessary, or which have a built in reward. Things like "bite", "up", "all gone", "outside", "drink", "what's that" or other things that are fun or useful.
So while variety may be important to a certain extent, babies LOVE repetition, and require repetition to learn effectively - the younger they are, the more repetitions they need to mimic something. Things that are familiar help them orient themselves to life, help them feel secure, and teach them relational concepts more quickly.
A reperatoire of 5-6 songs with motions that go with them is enough for a little one. Same with books. They learn fastest what they do over and over from the time they are first able to be coached through it.
I'm not one of those moms who takes her kids on daily nature walks and stops to examine the scientific lesson in every little thing, or who engages in heavy math experiments, etc. The thought of that kind of constant educational whirlwind just wears me out! I always was a casual teacher - just taking the logical opportunities that presented - pointing out the lessons when the dog had pups or when we planted the garden, or when Alex was diagnosed with Leukemia. I've raised seven very smart kids, all of whom have IQs close to or above the genius range, and all of who not only know things, but know how to LEARN things themselves. That balance is important.
Give your baby plenty of time to learn to entertain herself too - if you try to get in too much teaching, you'll deprive her of the opportunity of learning to find things within herself, and for herself.