Earlier this year, I simultaneously read Red Rising, by Pierce Brown (which I did not finish) and Red Queen, by Victoria Aveyard (which, spoilers, I did finish but did not enjoy.  At all.)  It was a surreal experience.  Both heroes are scrappy, low-in-the-caste system spitfires.  They both, through strange twists of fate, are forced to join the upper class, which they hate.  (Sound familiar?)  I admit, however, that although in both the lower classes are called Red, the upper classes are called Silver in Red Queen and Gold in Red Rising, so they're obviously totally different.  And, if you observe, 50% of the titles are different, which obviously invalidates my point that they're the same book with different character names.
Suffice it to say it was a surreal experience.  I was only able to finish one of them but felt like I've gotten the full experience of each.
Tons of books use the caste system these days.  It accomplishes two purposes.  First: it adds a lovely Asian influence, which has become quite popular in YA literature, without all that pesky research required for, you know, actual Asian influence.
Secondly, and more importantly, formulaic books are just more fun.
Understand that when I say formulaic, I don't mean it derogatively.  Perhaps 'highly structured' would be a better phrase.  It's not a bad thing at all.  Lots of books that I love are highly structured.
J. K. Rowling, for example, brilliantly utilizes the school system and school year to plot her novels.  This always seemed to me a terrific idea because, if she ever ran out of plot, she could go ahead and make it Christmas, then start again with a fresh semester.  In addition, the regularity of the school year, classes, and homework provide the perfect contrast to the magical curriculum, keeping the fantastic from becoming utterly strange.  Shannon Messenger uses this trick as well in her Keeper of the Lost Cities books.
Formulaic plotting accomplishes another feat by adding a time limit, which immediately adds urgency to the plot.  Rick Riordan's Percy Jackson series does this marvelously.  Every book has an expressed time limit, as well as the series' overarching deadline: sooner or later, Percy will turn sixteen, and all the prophecies at his birth will come true.  It gives the books awesome pacing.
As awesome as these formulaic approaches are, however, at the end of the day, they are just that: formulaic.  After approximately a thousand books formatted the same way, I have really grown tired of Rick Riordan's plotting.  J. K. Rowling used the same system for seven books, but she chose to depart from it when expanding the franchise into a movie spin-off, and I don't think that is a mistake.
So there, readers, are a few examples of highly structured plotting: the good, the bad, and the ugly.  Where do you stand on the matter?  How formulaic is too formulaic?