Your examples don't apply to a mortgage REIT. Essentially all of a mortgage REIT's assets are carried at fair market value, not cost or depreciated cost. At 3/31, CIM showed about $ 6.1 billion in total assets, and about $ 5.5 billion of this was carried at current market value. So for a mortgage REIT, book value is a pretty good approximation of fair value for the assets. In valuing the stock, you have to add some value for the business itself, so a bit of a premium over book is OK at times, but you can't ignore book value.