Book value is the accounting value of the company or trust, which includes intangibles (goodwill, etc). NTA is the value of the company or trust's net assets, not including the intangibles. REITs generally don't have many intangibles, so generally, for REITs I take book and NTA to be about the same - but keep in mind quarterly property valuations or more recent changes in cap rates and yields, as these obviously won't be reflected in last year's annual report.
