FA pays for your tuition and sends you a check for the remaining balance.
Imagine that you are getting $6000 in FA per year.
Imaginary numbers:
Tuition $1000/qtr ($3000 yearly)
Therefore FA will send you a $1000 each quarter approximately on the 2nd week of each quarter.
Check
http://www.csupomona.edu/~financial_aid/
for updated information about reimbursement. Sometimes (like Spring '05) disbursements will be delayed by 1-2 weeks.
To answer your question about books, most people do buy the books upfront with their own money (or credit card) and pay it off with FA.