I recommend reading of the following book (no, I don´t get money for advertising, I just like it! really!):
"Mass Spectrometry: A Textbook" 2nd corr printing, by Jürgen Gross, Springer Verlag, 2006. ISBN: 978-3-540-40739-3
"Massenspektrometrie: Eine Einführung" 5., completely revised and updated edition, by Herbert Budzikiewicz and Mathias Schäfer, Wiley-VCH, 2005. ISBN: 3-527-30822-9 (in german)
For people who have to deal a lot with interpretation of EI mass spectra, it may be a good idea to buy this one:
"Interpretation of Mass Spectra" 4th edition, by Fred W. McLafferty and Frantisek Turecek, University Science Books,
APCI (Atmospheric Pressure Chemical Ionization)
APPI (Atmospheric Pressure Photo Ionization)
CI (Chemical Ionization)
EI (Electron Impact)
ESI (Electrospray Ionization)
FAB (Fast Atom Bombardment)
FD (Field Desorption)
FI (Field Ionization)
GD (Glow Discharge)
ICP (Inductively Coupled Plasma)
LDI (LASER Desorption/Ionization)
LIFDI (Liquid Injection - Field Desorption/Ionization)
MALDI (Matrix-assisted LASER Desorption/ionization)
NSI (Nanospray Ionization)
B (magnetic sector)
E (electric sector)
FT (Fourier transform)
FTICR (Fourier transform ion cyclotrone resonance)
ICR (ion cyclotrone resonance)
IT (ion trap)
LIT (linear ion trap)
Orbitrap
q (quadrupole)
QIT (quadrupole-ion trap, Paul trap)
r-TOF (reflectron-TOF)
TOF (time-of-flight)
tq (triple quadrupole)