My daughter is 2 1/2 and she LOVES her Van Gogh book. Brings it to me all the time to read to her. In all the books there is great rhyming, short phrasing (for similarly short attention spans--great for toddlers!), and beautiful paintings.
My personal favorites are Degas and Van Gogh. I was rather let down by the Monet; I thought they chose works that didn't represent what Monet did best and was best known for, but no kid is going to care about that. They actually work together to tell a story, which is nice compared to the more randomly chosen paintings in other of these books.
The Matisse has some crazy paintings in it but they are bright and boldly colored, sure to capture a kid's attention. (Some people have complained about the two "nudes" in the Matisse book, but realistically, the figures are not anatomically detailed and in my opinion, not at all offensive or embarrassing.)
I love these because they familiarize children with famous works of art and artists without them even knowing it and the writing/poetry in the books is fun to read and keeps my daughter reading along. Highly recommended, as well as the other individually sold books (Seurat, Cassatt, Picasso, & Renoir)!