Foucault is difficult, but essential. For anybody seeking a way in, the series entitled 'Lectures at the College De France', beginning with Lectures on the Will to Know is perfect. Because the lectures were written for a lay public, the language makes his concepts much more accessible than does his academic writing. You can almost hear his voice in the presentations. In addition, the lectures distill what later become full-blown treatments. So one can get the essence of Foucault, and witness his development and change as a thinker, by reading the series in chronological order. That might now be possible with the publication of the above-mentioned 'Will...'.