This is a tricky topic because I'm not quite sure what they mean. Mr. Penguin and I read quite different books. Except for popular crime. We both enjoy some of those.
The illustrator I most love is Cecil Aldin. He was an Englishman who did countless illustrations of dogs, horses, usually fox hunting and English country scenes. I have several books with his illustrations and I never get tired of the drawings. He captured the expressions so well of dogs being happy, being sad, getting into trouble. They really are beautiful and often quite comical.
I hope you enjoy these.