It's 6 of Dr. Seuss's books, and ones that most people haven't heard of. If you actually look at the content of the books, they are clearly racist and demeaning to those they make caricatures of.
And in any case, it was not a sudden "canceling" or anything approaching that. Seuss's estate, managed by his family, made the decision after much deliberation to cease the publication of only six books due to the content. You could even see it as an anti-cancellation - Seuss's family wants to avoid him being associated with the obviously racist content of some of his work.