Simply great music, all of it rather mellow and cool; this music is what people think jazz is all about. It's so popular it's become sort of cliché, even.
Someone playing jazz today can hardly grasp the change this 'modal' stuff meant to the jazz scene, then, because today, we're taking it for granted that chords are scales and scales are chords, so to say. To me, playing the piano in "All Blues" (which is supposed to be modal jazz) or pre-modal jazz like "Caravan" is not really all that different.
The fascinating thing about this music is the simplicity of its concept. It doesn't take a master to play "All Blues" -- the theme is simple and an adequate accompaniment is not very hard to deliver either. This extreme simplicity, however, enables masters such as the stellar outfit that Miles Davis put together for this record to become immensely creative.
If you are prejudiced about how jazz is just the boring soundtrack to a neverending night in a cocktail bar, this album will not change your opinion. The last thing this will give you is a cheap thrill. But chances are you will enjoy it anyway.