It is possible to divide the document and to use book
A] Check to see how much memory InDesign is using when you have that
document open:
1) Click the pearl
2) type taskmgr
3) press enter
4) Sort the window by memory used - no doubt InDesign will be near the
top
B] Find out how much RAM your computer has
1) Press the Windows Key + Pause/Break to bring up system information
2) Amount of RAM listed in bottom right corner
Vista itself will use about 1 gig of memory. If you have other
programs open, even programs only loaded in the system tray by your
clock, you might be trying to use more RAM altogether than you have
installed. If that happens, Windows starts using a small piece of your
hard drive as Virtual RAM. Any program that dips into that Virtual RAM
area will slow down immensly, because your hard drive is 1000x slower
than your RAM is.
If you find that you should have an ample amount of ram available,
then it could be the Processor is the limiting factor - to help with
this, go back into taskmgr, and right click on the InDesign line - set
the priority to one setting higher than it is. Don't bother setting
InDesign to the highest priority as this will probably crash the
computer. I know you're going to now out of curiosity, but remember I
told you what would happen. :D