O'Reilly announced they are now selling one chapter of a book very similar to the buying songs online

(Buy O'Reilly Books by the Chapter) I am not sure how usefully this is typically songs stand quite nicely by them selves but a single chapter in a book?  For 3.99 a chapter it only takes about 3-4 chapters to justify buying the whole book.  I will admit I do have a few books where a few chapters were a waste of my time, sadly you have to read said chapter before you make that evaluation.  In music you hear the song on MTV, Radio, or Sirius.  How do I preview the chapter before I buy?