What boggles my mind is the exponential growth, depth, breadth and excellence of today's young adult fiction. That's as opposed to In My Day™ (a halcyon time that dates me terribly, but doesn't have me going all grumpy old crone just yet). In My Day™ it seemed like there was only Madeleine L'Engle, Choose Your Own Adventures, and Island of the Blue Dolphins. That wasn't all, but you get the idea.
Now? The term "YA" is no longer a four-letter word and is no longer synonymous with limiting, "childish" subject matter, fair-to-middling quality, or soft, weak niche sales. Quite the contrary. The market is booming. The writing is much more sophisticated. More so than standard adult fare often times. That demarcation line of "too old to be reading this" has blurred irrevocably.
Today's YA genres are more specialized & more vast - wizards (duh), dark fantasy, magic realism, horror, and even satire and hard sci-fi. And things like sexuality, gender identity, depression, murder, suicide, and death are routinely (often realistically) addressed as opposed to being exceptions to the rule. Subjects deemed suitable for YA's nowadays were rare or unheard of In My Day™.
And the quality of the books themselves — their construction, lavish illustrations, and packaging — represents a stylistic renaissance. The books look great on your shelves, like books you'd want to pass down from generation to generation, or discover when you're a kid to change your world forever.
Many reasons behind this YA boom are cultural or anthropological. Generally speaking, there are more kids out there. Tweeners happened, as well as "Teh Interweb" revolution. And the significance of a book released in 1997 introducing a character named Harry Potter cannot be discounted. For better AND worse.
Okay, my Rowling Rant: count me as one who surfs the tsunami wave of Potter backlash. But this stems from my three — yes, three — abandoned attempts to get through the first freaking book. Harry spent so much time dickering at the Wizard School Supply Store and the Bank that I couldn't be bothered, at page 100-something, to finish wading through thickets and thickets of Exposition by the Big Fat Wizard Guy & see him to finally get to his first class. And doesn't EVERY book start the same way (locked in his closet with his mean Muggle guardians, spirited away to the Wizard Bookstore, pages of Fat Guy Exposition)? Now a shelf of Potter books later, the "you should really give it another shot" ship hath sailed.