The purpose of this series is, if not entirely, at least primarily to teach kids coding. Well, a bit of coding. By the end of it you can do a lot of stuff with turtles in the Logo programming language, and you learn about some of the principles of coding.
Book 1: Secret Coders
Yeah, this is one of those series where the first book has the series title.
I really like how they used actual turtle-shaped robots for the in-universe turtle graphics. ("Turtle graphics" is a term for pictures drawn by having a pointer move around the screen drawing lines, rather than by some other means.) I'm pretty sure most of the series's initial audience wouldn't get that joke (as I didn't on my first read-through), but it's funny if you know what those are.
There's a character in this, Josh, who's... how do I explain Josh? His reactions to everything are funny, partially because he's kind of clueless but takes everything seriously. Except it's seriously-for-Josh, so he does things like ask the angry janitor to please not feed him to piranhas.
(Our other two main characters are Eni, a deuteragonist, and Hopper, the protagonist. Eni's the dark-skinned one, Hopper's the girl, and Josh is the one with weird spiky hair.)
Book 2: Paths & Portals
The title refers to Path Portals (in-universe, this means patterns on the floor where you have to program a turtle to walk around them in order to open up a secret door).
We get the first whiff of our minor antagonists and later minor allies the rugby team in this book. I'm not entirely sure why this presumably American school has a rugby team instead of, say, a football team, but it doesn't really matter.
We also get the first whiff of our first BBEG, Principal Dean. ("BBEG" is a roleplaying game term that stands for "Big Bad Evil Guy" [or, as necessary, "Big Bad Evil Girl"].) He's not actually in the "main villain" slot for very long.
Book 3: Secrets & Sequences
In which we're introduced to the Giant Flying Turtle which is actually a Giant Flying Laser Turtle. And in which Principal Dean gets kicked out of the villain chair by the actual villain of the series, Doctor One-Zero.
He actually has some interesting motivation. He used to be your bog-standard try-to-take-over-the-world supervillain with a robot army, but he's reformed. Sort of. Someone told him to use his super-genius status to make people happy, and he did. But by "make people happy" he means "give people a potion that rewires their brains so their sole desire is to see the color green."
Book 4: Robots & Repeats
This one sets up some stuff for later books, most notably the Turtle of Light (who is briefly named Josherella by Josh, before Eni names it Light-Light) and the fact that Doctor One-Zero's super potion, "Green Pop," does a supercharged Diet-Coke-and-Mentos thing when shaken.
This also reveals that Mr. Bee, the coders' mentor who I forgot to mention until now, has no nose and is from an alternate dimension. Which isn't Australia. (That bit will make more sense if you read the Favorite Lines section.)
There's a digression into ASCII encoding for a bit here, when the characters have to decode something written in ASCII.
Book 5: Potions & Parameters
This book ends with the protagonists about to use regular polygons to open a portal to another dimension, and that's rather a weird sentence.
And there are flying antigravity turtles. We use them, the new command we've learned that makes things go in circles, and the fact (established in Book 4) that Green Pop sort of explodes when shaken to ruin his stockpile truck of it. I don't think the flying antigravity turtles see much use in the final book.
Speaking of which,
Book 6: Monsters & Modules
The flying antigravity turtles do not see any use in this book.
The other dimension does get visited, though. It's Flatland (originating in
this book), a two-dimensional universe from which Professor Bee hails.
I really like that this series has an in-universe reason for the random coding challenges sprinkled throughout the books. It makes it to where they have a plot purpose rather than just "kids learn to code yay!"
Overall Notes
I should probably clarify: "secret coders" does not mean people who make secret codes, it means coders (i.e. programmers) who are secret.
These books are really rather short, enough so that I had trouble making some of the books' sections longer than a sentence or two.
If you want to get someone interested in coding, these books would probably be a good vector for that.
The art is by Mike Holmes, who also did the art for the Wings of Fire graphic novel series.
Were this a videogame, I'd rate it: A soft E10+ for some cartoon violence.
4 stars.
Favorite lines:
"Who are we?"
"Stately Academy Rugby!"
"And do we fear anything?"
"Well--"
"Usually not--"
"but snakes--"
Page 65, Paths & Portals. It's the rugby team.
Mr. Bee: "Where I'm from, noses are rather rare."
Eni: "And where is that, exactly?"
Josh: "Australia!"
Hopper, facepalming: "Such a dummy."
Page 9, Robots & Repeats. Follows close upon the reveal of Mr. Bee having no nose.
"Ducks aren't supposed to have teeth! That's cheating!"
Page 89, Robots & Repeats. Josh, reacting to a duck-shaped robot which suddenly revealed that it has teeth.
"You kids are taking Advanced Chemistry?"
Page 31, Potions & Parameters. It's a random NPC doctor who doesn't believe that those kids are taking Advanced Chemistry. (My high school course in Advanced Chemistry caused me to quote this relentlessly for a few weeks.)
"With regular polygons, we're going to open a portal to another dimension!"
Page 79, Potions & Parameters. This one is Mr. Bee.
"Quiet, B. Square!"
Page 89, Monsters & Modules. It's the Circles from Flatland, who've been convinced that Doctor One-Zero is actually escaped criminal B. Square.
(Endnote: Despite what you might think, there isn't a secret seventh book named Dungeons & Dragons.)