My formula for deciding when I can put down a book

How accessible and attention-grabbing do books need to be?  My personal theory of literature (credentials, B.S. in English, BYUI; future prolific author; extensively read--including War and Peace, James and the Giant Peach, and Reader’s Digest) dictates that the very best works would of course have interesting openings.  In practice, however, how many times do I nab a supposed classic and find myself snoring through hundreds of pages of absolutely unADHD-friendly delayed gratification?  Look, if we want and expect kids to keep reading for the sake of reading (perhaps a faulty premise), we need to feed them more saccharine laced fluff more along the lines of Twilight, Goosebumps and Everyone Poops! 
I have extra power such as pride and guilt that gets me through some of the most mundane novels, but we all know kids nowadays (and adults too) can’t be trusted to possess such valuable attributes.  It would be nice to know that you gave a book your best effort and at the same time remove the stigma of leaving a  book unfinished.  Therefore I determined that I personally would develop a formula for when I could put down a novel with a dragging plotline and still maintain a modicum of respectability. 
At first I thought I might settle on an arbitrary number, such as  one-hundred pages in.  But that is unfair to longer books, so then I decided that it must be a percentage.  Of course there are books that reward you for sticking around, but there are also clunkers that leave you scratching your head, wondering why you wasted so much time.  I feel that if you read half of a book, you should be moderately far into a plot by then, so that would be too far and too much reading to set as a benchmark.   A quarter of a book is more reasonable, but I am a literary snob so I will err on the side of the author and compromise with 33%.  Think it out:  if a book does not speak to you on some level after a third has been read, you can safely put it down.  It’s fair.  It’s only right.
Then I got to thinking that I need to have a reason to put the book down, more complex than that it is simply too boring.  So I devised this protocol:  after 11% of the book has been read and there is any tangible feeling that I do not want to continue (manifested by yawns, periods of two days or longer of inactivity, or rampant debauchery) I will draft a first warning that details the setting, plot and characters; after 22% of the book has been read and the feeling continues I will draft a similar warning along with any additional developments, and then at the 33% mark I will write a third and final summary, after which I can safely determine that the book is too boring and I can move on.  Now, if the first feeling that I want to quit is after the 33% mark, only one report is needed.  The same rule applies if the first feeling of quitting is between the 22% and 33% marks, except only two reports are needed.  If these rules are followed, all feelings of guilt will be expunged and all pride will be upheld.  If these rules are broken, guilt shall be doubled and pride will be taken away, even that which I already have.