The adult editions started releasing in 2004, replacing the original adult editions. The adult editions feature simplistic designs to appeal to an older audience and were published in hardcover and paperback. In 2015 Bloomsbury released a new set of adult editions.
Harry Potter Set: Adult Edition: Rowling, J. K.: 9781408898659: : Books
Harry Potter Set: Adult Edition: Rowling, J. K.: 9781408898659: : Books
HARRY POTTER: Adult Editions: Books: Bloomsbury Publishing (UK)
Harry Potter Extended Versions — Harry Potter Database
rowling - harry potter set adult - AbeBooks
Harry Potter Adult Editions 2004 — Harry Potter Database
Harry Potter Set: Adult Edition: Rowling, J. K.: 9781408898659: : Books
Harry Potter Extended Versions — Harry Potter Database
Why Are Harry Potter First Editions So Expensive?, 51% OFF
Harry Potter Extended Versions — Harry Potter Database