As a librarian, I am of the opinion that all reading should be encouraged. Whether it is Young Adult, New Adult, romance, graphic novels, eBooks, audiobooks, or anything else, reading is reading. Not all reading will be deep and thought-provoking, some is just for fun or more casual. Even adults who are learning a new language might decide to read children's materials in the other language. While it may not be extremely challenging or complex, it is still reading.
First, we as librarians should make sure our own personal beliefs on what is "real reading" not interfere with assisting patrons find the materials they want and may enjoy. We can work towards encouraging adult patrons who enjoy Young Adult literature and graphic novels by including these types of items in our regular reader's advisory for patrons. We could incorporate these types of materials into our adult displays and suggest them to patrons in reader's advisory interviews. While some patrons might reject our YA or graphic novel suggestions, some might be interested in checking out these collections.
I also liked the "It's OK" sign from this week's prompt post. Having a display with YA materials and this sign would be a simple way to use passive reader's advisory to encourage patrons to check out the YA collection while letting them know we will not judge them for checking out these materials. A similar display could be made for graphic novel items.