What reading level is the Nonfiction-Grades 4-8 (Millbrook Press) series?

The Nonfiction-Grades 4-8 (Millbrook Press) series by Rebecca E. Hirsch is at a Grades 5.5–6.8 reading level (average Grade 6.1). Intended for Middle Grades (Ages 9–12). There are 5 books in the series.

What order should I read the Nonfiction-Grades 4-8 (Millbrook Press) books?

The Nonfiction-Grades 4-8 (Millbrook Press) series has 5 books in order: 1. Little Monsters of the Ocean, 2. Masters of disguise, 3. Monarchs Are Missing, 4. Secrets of the sky caves, 5. When Plants Attack.

What age is the Nonfiction-Grades 4-8 (Millbrook Press) series appropriate for?

The Nonfiction-Grades 4-8 (Millbrook Press) series is recommended for Middle Grades (Ages 9–12). The average content intensity is 1.2/5.

Nonfiction-Grades 4-8 (Millbrook Press) Books in Order

5 books by Rebecca E. Hirsch. Reading level: Grades 5.5–6.8. Middle Grades (Ages 9–12).

Series books grow with readers — but that's also the trap. Most series start at one reading level and one content intensity and drift upward over the course of the run. Nonfiction-Grades 4-8 (Millbrook Press) (5 books by Rebecca E. Hirsch) lands at reading level Grades 5.5–6.8, with average content intensity 1.2/5. Intensity stays consistent across the series — a kid who can handle the first book can generally handle the rest.

The reading-order table below lists every book with per-volume reading level and intensity badges so you can spot any escalation before it catches your reader off guard. For a deeper dive into how we score text difficulty vs. emotional weight separately — and why series readers especially benefit from that split — see our methodology page.

Books

Grades 5.5–6.8

Reading Level

1.2/5

Avg. Intensity

Middle Grades

Content Intensity Across the Series

Consistent

Content stays at a steady intensity level throughout the series.

First book Latest book

Nonfiction-Grades 4-8 (Millbrook Press) Reading Order

#	Title	Reading Level	Content
1	Little Monsters of the Ocean Heather L. Montgomery	Level 5-6	Gentle
2	Masters of disguise Rebecca L. Johnson	Level 6-7	Gentle
3	Monarchs Are Missing Rebecca E. Hirsch	Level 6-7	Gentle
4	Secrets of the sky caves Sandra K. Athans	Level 6-7	Mild
5	When Plants Attack Rebecca E. Hirsch	Level 5-6	Gentle

All Nonfiction-Grades 4-8 (Millbrook Press) Books

Little Monsters of the Ocean

Heather L. Montgomery

Little Monsters of the Ocean

Heather L. Montgomery

Level 5-6 Gentle

Masters of disguise

Rebecca L. Johnson

Masters of disguise

Rebecca L. Johnson

Level 6-7 Gentle

Monarchs Are Missing

Rebecca E. Hirsch

Monarchs Are Missing

Rebecca E. Hirsch

Level 6-7 Gentle

Secrets of the sky caves

Sandra K. Athans

Secrets of the sky caves

Sandra K. Athans

Level 6-7 Mild

When Plants Attack

Rebecca E. Hirsch

When Plants Attack

Rebecca E. Hirsch

Level 5-6 Gentle

Questions about the Nonfiction-Grades 4-8 (Millbrook Press) series

What reading level is the Nonfiction-Grades 4-8 (Millbrook Press) series?: The Nonfiction-Grades 4-8 (Millbrook Press) series by Rebecca E. Hirsch is at a Grades 5.5–6.8 reading level (average Grade 6.1). Intended for Middle Grades (Ages 9–12). There are 5 books in the series.
What order should I read the Nonfiction-Grades 4-8 (Millbrook Press) books?: The reading-order table above lists all 5 books with per-volume reading level and intensity ratings. Start with book 1 and read in publication order unless the table indicates a different recommended order for newer readers.
What age is the Nonfiction-Grades 4-8 (Millbrook Press) series appropriate for?: The Nonfiction-Grades 4-8 (Millbrook Press) series is recommended for Middle Grades (Ages 9–12). The average content intensity is 1.2/5. Check the intensity trajectory above to see whether content gets heavier across the series — if it does, sensitive readers may want to stop earlier in the run.