I think it varies - Lamb's Tales from Shakespeare was, as a child, my first introduction to the bard and one which I enjoyed immensely. My familarity with the tales helped my later readings of the Shakespeare at school.
Remixes and updatings are also all fair game I reckon. But condensing I'm less sure about - and where do you draw the line? 400 pages is still a hefty read - perhaps 280 would be better?
For the original - Mobileread itself offers a Kindle friendly edition too: