Hi Cathryn,
Yes, NAV/BC requires the Depreciation Book Code and it's okay to use the default book.
And then ... for "land" you can select the Depreciation Method = "Manual" instead of "Straight Line".
This allows you to register the acquisiton costs (no check for a missing Depreciation Method) but does not force you to calculate any depreciation (still ... if needed at some point / for some reasons you can depreciate manually).
If you cannot change the Depreciation Method becasue you already registered the acquisiton costs ... please temporarily enable "Allow Changes in Depr. Fields" in the Depreciation Book, change the Depreciation Method in the fixed asset record and then disable the "Allow Changes ... " again.
Hope this helps
Kind regards
Dirk