How to deal with xpath's Comparison expression ?

Hello everyone:
	I am doing a selection from an xml file.This file looks like:
<bookstore>
<book category="WEB">
  aaabbb
  <title lang="en">Learning XML</title>
  <author>Erik T. Ray</author>
  <year>2003</year>
  <price>39.95</price>
</book>
<book category="WEB">
  <title lang="en">XQuery Kick Start</title>
  <author>James McGovern</author>
  <author>Per Bothner</author>
  <author>Kurt Cagle</author>
  <author>James Linn</author>
  <author>Vaidyanathan Nagarajan</author>
  <year>2003</year>
  <price>49.99</price>
</book>
</bookstore>

How can I find out the node which contains the "aaabbb" text using " = "
expression?
I build the xpath like : /bookstore/book[text()="aaabbb"]
But that doesn't work.

Thanx a lot for your help!