I made this thread a sticky. If you can memorize all the notes Brian posted and know Ohms law
V = I x R (Voltage = Current multiplied by Resistance)
R = V / I (Resistance = Voltage divided by Current)
I = V / R (Current = Voltage Divided by Resistance)
you will pass the technicians. You don't necessarily need the book but it can help and probably recommended as a reference and further explanation of concepts.
Read the notes, take some practice technician exams at qrz.com
Find a place to take the test at aarl.org