As a child I remember thinking that adult books were so boring. Just a lot of text and no pictures.
So few adult books are illustrated, and it is a shame. Grown ups can enjoy pictures just as much as children.
Luckily, I have a great edition of the Hobbit and one of the Spiderwick Chronicles, both with inked drawings. And I look at them much more frequently than my other books.
The story I am writing now is about a lot of different horses, and as I love to draw I just have to draw some of them.