Multi Book Accounting Assuming that our customizations, integrations and reports do not have to consider accounting books, is it safe to say that we do not need to fully test them because they'd default to the Primary Accounting Book anyway once we turn on and set up FULL Multi Book Accounting?

That's my experience using Multibook. If you don't explicitly define/select the Accounting Book in the report, script, customization, etc. then its business as usual. Our only hiccup was Amortization Journals because those are Book Specific and we need to manually generate them for each Accounting Book.

true - if you do not have different rev rev and expense recognition; also there is FAM with its FAM implementation again

Thanks for the confirmation.