How to alter your voice?
Do you mean speaking or singing? Voice work is studied by both actors and singers, so yes, there are books out there, but I would recommend finding a good teacher since it gets very technical and you really have to have a clear understanding of anatomy and physiology and how everything fits together before you can try to do anything to it.
Be careful of expectations though. Everyone is pretty much born with a particular %26quot;comfortable%26quot; range. A good voice teacher can help you find yours. It may be the case that you've been speaking/singing too low or too high, and that can be adjusted, but if you just want a lower/higher voice and it's not something that is natural, you can actually damage your vocal cords.
Check into local acting classes or even the theatre department at your local university to find vocal teachers.
How to alter your voice?
are you mono-tone...
