I’m preparing some book recommendation lists (finally), and I think it would be handy for folks to have this information for reference. These are the rough definitions used in the marketing and packaging of books intended for a younger audience. Keep in mind, some publishers and book stores may be more liberal with these definitions, and that these do change over time, some folks splinter these groups even further, and that these designations are subjective as heck.
Picture Books – target audience is age 3-8
These have great pictures and very few words (and some have no words at all).
Early Readers – target audience is age 4 and up
Also sometimes called easy readers. These include my entire collection of Dr. Suess books. These still strongly feature pictures.
Middle Grade – target audience is age 7-12
Sometimes called intermediate readers, or early chapter books. We used to have two or three genres for this age group, but they’ve really blended together in the last 10 years or so, which is a bit unfortunate. You’re going to find a wide range of complexity here. The easier (emergent reader) end of the scale includes books with 1-2 page chapters and occasional pictures, running right around 75 pages in length. The more traditional middle grade end of the scale books have more complex plots and longer chapters, and run around 320 pages. The first three Harry Potter books are technically a middle grade.
Classic Young Adult – target audience is age 12 and up
This genre is a bit of a mess. It includes a lot of classic literature that has been repackaged for younger readers, things more complex and longer than the middle grade work, and all those teen books that don’t quite tread into the controversial topics of 14 and up books. Books four through seven of Harry Potter tend to go here, as they are longer and more complex than their middle grade counterparts, and they have more graphic violence, but they aren’t quite sexy or violent enough to go in the next category.
14 and Up Young Adult – target audience is age 14 and up
Sometimes referred to as gritty YA. These are likely to have more on screen sexual content, controversial content, and graphic violence. You’re also likely to find books that would be labeled as classic YA if not for their GLBTQ characters (this is a stupid thing, I know, I’m the wrong person to complain to).
New Adult – target audience is age 18-30
Think of this as 14 and up YA, but for people who are now considered adults, and are trying to do the whole adulting thing for the first time. Themes focus on finding yourself, leaving home, developing sexuality, negotiating education and career choices, and college and dating mishaps.
My YA work tends to fall in the classic and 14 and up YA camps. My adult work tends to fall in the new adult category mostly due to protagonist age and the tone or voice of the narrative. Though I wasn’t as familiar with them, it looks like no one uses “intermediate readers” or “ten and up” to refer to genres anymore, though they used to be distinct and commonly used categories.