Just last night my husband and I were talking about books and how our son had a favorite book when he was a toddler, Dig, Dig, Digging by Margaret Mayo, that one of us literally read every-single-night from July (when he got the book for his birthday) to probably Christmas time. Around Thanksgiving we realized that he could recite the book by himself by simply looking at the pictures.
It got me to thinking about my two year old daughter and how she doesn't really have a favorite per se. Pretty much we read the same book for 1-2 weeks until she memorizes it and then we move on to the next book. Her current favorite is Alligator Alphabet written by Stella Blackstone and illustrated by Stephanie Bauer. I'm a huge fan of this book largely because of the pictures, I know I'm a sucker for illustrations, but also because of the simple text "Aa is for alligator" etc.
Each night I read the book through first and then we flip backwards through the book and I ask my daughter what each letter is. She is slowly working on telling me the names of the animals in the pictures and repeats the letter if she guess incorrectly. She knows 4 or 5 letters consistently, but always tries to figure out the others. I also really love the double page spread of all of the alphabet letters at the end of the book, which is a great review of the animals and letters. We play "Where's the....?" with the last page. It's a great book for starting to introduce letters to toddler learners or for just reading and enjoying.