By JoeWalker on

I've been getting an error message "SELECT DISTINCT, ORDER BY expressions must appear in select list" and tracked the problem down to book.module line 825.

I made the error message go away by adding "b.weight" to the SQL.

I'm new to Drupal and I don't even know PHP properly so I have no idea if this is the right thing to do, but it looks like a fix that you may need to know about.