What reading level is City of Glass?

City of Glass by Cassandra Clare is at a Level 4-5 reading level (Lexile 760L). Recommended for Middle Grades readers (Ages 9-12).

What age is City of Glass appropriate for?

City of Glass is recommended for Ages 9-12. HootRating: 9LP (Light — Physical).

What genre is City of Glass?

City of Glass is fiction — Juvenile Fiction.

Does City of Glass have any content warnings?

City of Glass has a HootRating of 9LP (Light — Physical). No specific content flags noted. On HootRated, every book is rated across four dimensions — emotional, physical, social, and thematic — to help parents make informed choices.

How many pages is City of Glass?

City of Glass by Cassandra Clare is 541 pages.

Reviewed by HootRated editorial · Last updated July 16, 2026

City of Glass

Cassandra Clare

City of Glass

Age Rating, Reading Level & Content Guide

The Mortal Instruments Book 3

by Cassandra Clare

Reading Level 4-5 9LP Ages 9-12 Balanced Read

The text is written at a 4th grade reading level, the subject matter is intended for middle graders (ages 9–12), and the content is mild with minimal sensitive material.

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About This Book

Here's a secret: Simon is no ordinary vampire—he shines in the daylight and holds the key to peace between two very different worlds. But when mysterious murders stir up trouble, Simon must step into the shadows to solve the mystery. And that's only the beginning.

Themes

SupernaturalFictionMagicVampiresDemonologyMystery Adventure

Quick Assessment

City of Glass follows Simon, a unique vampire who can walk in daylight, as he navigates a supernatural world of Shadowhunters and Downworlders. The story includes themes of magic and mystery appropriate for middle-grade readers aged 9-12, with some mild fantasy violence and suspense. Parents should note the supernatural elements and occasional peril but can expect an engaging, fantastical adventure.

Why we rated City of Glass 9LP

City of Glass is written at a Level 4-5 reading level with a Lexile measure of 760L across 541 pages. Strong independent readers around grade 5.5 can typically handle this book on their own; with parent or teacher support, City of Glass works for readers up to grade 6.5.

We rate City of Glass as 9LP ("Light — Physical") because the content sits in the "Mild" range — mild conflict — the kind a child encounters in normal play and sibling life. Across our four dimensions (emotional, physical, social, thematic) the book reads as evenly mild; no single dimension stands out as a concern.

No specific content flags were raised by community reviewers, which is consistent with the mild intensity score.

Thematically, City of Glass explores supernatural, fiction, magic, vampires, and demonology — these threads give the book room to mean different things to different readers.

Good fit for

✓ Children in the Ages 9-12 range — the maturity and attention span match the story's pacing.
✓ Kids drawn to stories about supernatural, fiction, magic.