My 6x9 paperback is 1/8" short on both length and width. Is that normal? Doesn't seem like much, but I really needed that for my top and outside margins.
There is always a bit of variation in the final trim size of a book.
We suggest that nothing of importance be within a quarter inch of the book cover's edge. You can download the 6x9 template file for a visual representation of the "danger" zone.
The only thing within 1/2" inch is white space, but I don't think I would call white space "nothing of importance" as even just that 1/8" can make a huge visual difference.
Is it at least consistent? If I slid my text frames down and over, would the next copy be different but just as off?
Yes tcw, it's consistent.
When you preview your cover there is a trim line showing so you can check if your graphics are going to be cut or not. Be sure to check there.
After using Lulu for a good while I have learned to keep my content (on the covers too) well away from the edges, but even so I see many mass-produced books with even wider margins and it does not bother me one bit.