This is a common misconception. Particularly among experienced and well informed professionals like yourself.Quote from tomcole:
Book value is the easiest thing to fudge.

Book value is paid-in equity plus all retained earnings. The only way book value can be manipulated is by manipulating earnings first. Furthermore, most manipulation of earnings is done by moving accounting items through time, rather than simply inventing them, so in the long run book values are far more reliable than earnings.
Technically, book value also excludes intangibles such as goodwill. Of course, this makes book value even harder to fudge compared with earnings.
Hope that helps.
Martin