This is a book of poems, written in tribute to the poetry of William Blake. I wasn't familiar with Blake's work beyond "Tyger, Tyger", and actually went back to the library to find a volume of his work to better understand how A Visit was related to its namesake's poems. In the end, I understand. The guests at William Blake's Inn are familiar characters from Blake's own work, and most importantly, your mind does the same kind of somersaults in each!
I'll admit I'm not a poetry person generally, so even with my extra research a lot of this book is probably lost on me. But I did have fun reading it, and I loved the illustrations. I should note that while the poems are clearly inspired by Blake's work, the illustrations are not related to his artwork at all - but they are charmingly done by Alice and Martin Provensen in Colonial style, and there's a reason the book also won the Caldecott Medal that year.
I think kids would enjoy this book, if they like word pictures; there are some wonderful ones. The Man in the Marmalade Hat, for example, who is the embodiment of spring (cleaning and all!), and the King of Cats ordering his breakfast (involving Brisket of Basilisk Treat - what's not to love?). The story line is very loose, and this might bother some readers, but I think the positives far outweigh the negatives. I give it an 8.5.
Fun thing: the jacket tells us that while writing this book, Ms Willard actually built a six-foot model of the Inn, complete with prints of Blake's work on its walls and the residents mentioned in the book, and kept it in her living room!