If you count the pages you are likely missing exactly 32 (or perhaps 64) pages.
Every once in a while the bindery machinery skips a beat and binds in a blank
signature.  Sometimes you will find duplicate or missing signatures.  And in
particularly perverse instances, bindings that have different titles than the
material inside.
 
Cal Pryluck
Dept of Radio-Television-Film
Temple University
<PRYLUCK@TEMPLEVM>