i would take care with the label "normal".
although thalberg´s post is correct, i might add something.
nowadays, there are so many distinct approaches, used isolate or conjunct, that think of gradual harmonic analysis (the one thalberg pointed out, and the one that is most commonly teached in harmony courses) as the normal, or only method is a very narrow look at the analysis universe.
thierry, if you want an introduction to hardcore analysis (including schenker's), probably the best book is nicholas cook´s
a guide to music analysis. although superficial (regarding the actual theories), it requires a very solid musical theory background, otherwise it´s hard (or even impossible) to read.
after this one, the path leads to the authors themselves: schenker, reti, meyer, forte. in the case of the former, go for
five graphic analysis,
harmony and
der freie satz. well, after that and tons of music analysed, you would have a slight idea of what him was all about...

ps: it´s highly reccomended an unabridged knowledge of german language, and reading his original works, even better if you get the manuscript source...

ps2: if all you want is a general notion of his theories, there is a
site that can help you a bit.
