It differs the same way subjects differ, your purpose.
As an aside. People don't really read self help books the majority are shelf help.
ON average people spend about an hour reading a book that gets them to about the 3rd chapter in most books. By no means covering all that one might find in a book. A PhotoReader could go through the whole book in that time and get much more from the books.
It doesn't matter whether articles are related to each other; chapters of books are often unrelated, that's why they are separate chapters.
Post viewing is for building your curiosity and deciding where you want to begin and discovering how the book can satisfy your purpose.
Alex
