You only need to have the author name once. If you want the primary and the secondary to show on the same line, you'll have to do something like this:
1. Create a second detail section. Put the author name in this section so that it is NOT under the author name in the first detail section. (We're going to line them up side-by-side.)
2. Right-click on the author name in this new section and select "Format Object". Click on the Suppress formula button and enter something like {BookAuthor.AuthorType} <> 'Secondary'.
3. Format the author name in the first detail section the same way except the Suppress formula should be something like {BookAuthor.AuthorType} <> 'Primary'.
4. Open the Section Expert and for the first detail section select "Underlay Following". For the second detail section make sure that "Suppress Blank Section" is NOT checked.
If you want the author's names to appear underneath each other with some text about whether it's the primary or secondary. Set up one detail line with just one author's name. Create a formula that looks something like this: if {BookAuthor.AuthorType} = 'Primary' then 'Primary Author' else 'Secondary Author'. Use this formula on the report instead of just a text block.
-Dell