Stuart Levine of Tax Law & Business Commentary posts letters to the IRS (here and here) from pracitioners requesting clarification that Circular 230 does not cover certain opinions and documents, including tax books and articles:

We have seen it reported in the tax press that you and other IRS and Treasury Department officials have stated at public conferences that articles, training outlines and presentations and books are not covered opinions. Nevertheless, we understand that some practitioners are still concerned that these types of materials may be seen as containing “tax advice” because they explain how the law works and often include hypothetical fact patterns followed by an analysis of how the law applies to the hypothetical facts. They may even address the facts of a real case, such as a case that was the subject of a court decision, an IRS ruling or a news story. We believe that it would be inappropriate to interpret the rules to cover such materials. These are clearly intended to be educational, not to transmit advice. While it is true that other practitioners and taxpayers may often refer to such materials in formulating a view as to the actual consequences to a specific taxpayer of a given transaction or situation, these materials are not themselves “advice.”