But a ballpark scale can be quite helpful for some readers. Below are the terms I'll use and what they mean. Think density: thematic/literary content, length, maturity-range, etc. Most of what I post here will be middle grade fiction, generally aimed for an audience between 8 and 14 years. Young adult fiction sometimes contains R-rated content and if I decide to write about any YA books, I'll make that clear.
Light -- May be well-suited to younger or less proficient readers. Stories may be shorter and simpler. Think Ramona Quimby.
Medium -- Average middle grade fiction. Think Harry Potter.
Heavy -- The story may be longer, more intricate or contain thematic material better suited to more mature readers. Think Lord of the Rings.
*These rankings are entirely my own and completely subjective. You can look at reviews from entities like School Library Journal for more authoritative age and reading level guidelines.
The categories below have to do with content. A book may contain more elements than I tag in my review; I'll stick with the most prominent features.
Voices Outside the Mainstream -- This one is so important it gets its own post and an acronym (VOM). Short answer: diversity. See my post Voices Outside the Mainstream (and why we all need to listen).
Resilient & Resourceful -- Expect child characters who not only triumph over adversity but who reveal strength, intelligence, leadership, kindness and/or other talents far beyond your standard hero trope.
Catharsis -- Tear-jerkers, or a treatment of emotional healing and/or personal understanding. I'm stretching the literary term here.
Ecovalues -- Let's save the world, people! These books will get you thinking about being green and the moral implications of being part of a larger ecosystem.
Historical/Political -- Do you like books that give you an experience of life at another time? These books either reflect specific times in history or deal with political themes (usually both).
Meta -- Stories that comment upon themselves or about storytelling itself. A tiny favorite by Jane Yolen:
"Story," the old man said, looking beyond the cave to the dragon's
tracks. "Story is our wall against the dark." he told the tale: the landing,
the first death, the second. They heard the rush of the wind, the terrible
voice, a scream, then another. Beyond the wall, the dragon waited but
could not get in.*
Faery, Fantasy, Folklore -- Had to make my personal favorite both alliterative and acronym-izeable: FFF. Essentially a fantasy story, likely rooted in myth or folklore and may or may not involve faeries.
Goth -- Will probably contain FFF elements, but is also scary.
Sci-Fi -- Quick link for Science Fiction fans.
HA HA funny -- At least I had some good laughs while reading, and you might too!
Graphic Novel -- Just to make it easier for afficionados (like me) to find them.
Read Aloud -- Some books are better than others for reading out loud together. I may or may not have personally tested these but I sure did think while reading, "This would make a great read aloud."
* Yolen, Jane. Here There Be Dragons. 1993.