What reading level is the Pebble Plus; Exploring the Galaxy series?

The Pebble Plus; Exploring the Galaxy series by Thomas K. Adamson is at a Grades 1.4–2.3 reading level (average Grade 1.9). Intended for Lower Grades (Ages 5–8). There are 13 books in the series.

What order should I read the Pebble Plus; Exploring the Galaxy books?

The Pebble Plus; Exploring the Galaxy series has 13 books in order: 1. Astronauts, 2. Earth (Pebble Plus), 3. Jupiter (Pebble Plus), 4. Mars (Pebble Plus), 5. Mercury (Pebble Plus), and 8 more.

What age is the Pebble Plus; Exploring the Galaxy series appropriate for?

The Pebble Plus; Exploring the Galaxy series is recommended for Lower Grades (Ages 5–8). The average content intensity is 1/5.

Pebble Plus; Exploring the Galaxy Books in Order

13 books by Thomas K. Adamson. Reading level: Grades 1.4–2.3. Lower Grades (Ages 5–8).

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. Pebble Plus; Exploring the Galaxy (13 books by Thomas K. Adamson) lands at reading level Grades 1.4–2.3, with average content intensity 1/5. 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 1.4–2.3

Reading Level

1/5

Avg. Intensity

Lower Grades

Content Intensity Across the Series

Consistent

Content stays at a steady intensity level throughout the series.

First book Latest book

Pebble Plus; Exploring the Galaxy Reading Order

#	Title	Reading Level	Content
1	Astronauts Thomas K. Adamson	Level 1-2	Gentle
2	Earth (Pebble Plus) Thomas K. Adamson	Level 2-3	Gentle
3	Jupiter (Pebble Plus) Thomas K. Adamson	Level 1-2	Gentle
4	Mars (Pebble Plus) Thomas K. Adamson	Level 2-3	Gentle
5	Mercury (Pebble Plus) Thomas K. Adamson	Level 2-3	Gentle
6	Neptune (Pebble Plus) Thomas K. Adamson	Level 1-2	Gentle
7	Pluto Thomas K. Adamson	Level 2-3	Gentle
8	Pluto (Pebble Plus) Thomas K. Adamson	Level 2-3	Gentle
9	Saturn (Pebble Plus) Thomas K. Adamson	Level 1-2	Gentle
10	Stars Thomas K. Adamson	Level 1-2	Gentle
11	The Sun Thomas K. Adamson	Level 1-2	Gentle
12	Uranus (Pebble Plus) Thomas K. Adamson	Level 1-2	Gentle
13	Venus (Pebble Plus) Thomas K. Adamson	Level 1-2	Gentle

Level 1-2 Gentle

Venus (Pebble Plus)

Thomas K. Adamson

Venus (Pebble Plus)

Thomas K. Adamson

Level 1-2 Gentle

Questions about the Pebble Plus; Exploring the Galaxy series

What reading level is the Pebble Plus; Exploring the Galaxy series?: The Pebble Plus; Exploring the Galaxy series by Thomas K. Adamson is at a Grades 1.4–2.3 reading level (average Grade 1.9). Intended for Lower Grades (Ages 5–8). There are 13 books in the series.
What order should I read the Pebble Plus; Exploring the Galaxy books?: The reading-order table above lists all 13 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 Pebble Plus; Exploring the Galaxy series appropriate for?: The Pebble Plus; Exploring the Galaxy series is recommended for Lower Grades (Ages 5–8). The average content intensity is 1/5. 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.