The respective links below will take you to specific errata for hardback and paperback versions of "Computer-Aided Reasoning: An Approach". Feel free to report errors on the acl2-help mailing list.
See the General Errata for Books About ACL2 and Its Applications for general comments about how the evolution of ACL2 over the years can affect explanations or solution scripts. In particular, as noted there, some solutions may require inclusion of the following two events early in the session.
(include-book "ordinals/e0-ordinal" :dir :system) (set-well-founded-relation e0-ord-<)