As I re-read what was probably my favorite childhood series, my reviews will most likely be different from how I usually discuss books.
I'd like to start out by explaining why.
Keeper of the Lost Cities was the first book series Little Abby read that didn't have an animal on every cover, and it might have been the series that got me into fantasy (I say might because I don't remember if I read this before or after the Lost Heroes series by Riordan). Therefore, I have to give credit where credit is due and for that reason, I don't feel comfortable rating this series with my opinions as someone who is no longer a fifth grader.

I don't really have a plan for any of these reviews besides sharing the notes I took on the books in the Notes app on my phone, which I'll add at the bottom for anyone who is interested. They're mostly going to be me pointing out stupid details and pointing out the details the author forgot in the decade it's taken her to write the series thus far. Shannon, I'm begging you. Please. End the series. I don't need bonus novellas; I need closure.
But I briefly wanted to mention, upon my 8th(?) reread, what I think drew me to this series.
Look, in hindsight, there are parts of it that are kind of cringy. Sophie is very much a "not like the other girls" protagonist in this one, and she ends up in the healing center more times than I bothered counting. But all things considered, it also has a lot of my favorite tropes? Found family is the big one (especially in later books), but I've always loved magic systems with multiple types of magic. I also can't deny that there a variety of Keeper "things" that keep finding their way into my own writing and I can't make it stop (the most notable being: blue eye descriptions, freaking Fitz himself, and the clothing choices).
But that's enough of my ramblings for now. I'll include my notes below, and they may contain spoilers for future books, just a heads up.

Book 1 Notes:
- Literally, why didn't Sophie's parents homeschool her or try to find an online school if she hates public school so much...
- Also, as far as I'm aware, no one has gone on dinosaur field trips for, like, 30 years
- So, with the screaming children in the museum, Fitz didn't block out their voices despite being such a "strong" telepath
- First of all, Sophie just ran from a hit-and-run scene (pg 13)
- "He shrugged. 'Laws are rarely broken'" (22) - right, and that's why this entire series exists
- GETHEN WEARS SPANDEX (41)
- "'Kidnapping is a human crime. I've never heard of an elf even considering such a thing - much less trying it'" (51) - not Alden giving the Neverseen ideas
- Not Alden telling Fitz, "You've never had to watch someone fade away," too.. buddy is just predicting the whole plot
- Bronte is shorter than Oralie and Kenric (58)
- In addition to the Offish, the Vackers just have a random conservatory? Why? (117)
- Is Juline having human movies an early indicator of her allegiance to the Black Swan? Or is it just a coincidence? (154)
- Marella "girls are annoying" Redek (173) is like the only potentially canon lesbian
- (254) what did Valin do to get detention? I'm just curious...
- "No Empaths were THAT powerful" in reference to Keefe being able to sense her emotions from across the room... is that Sophie's doing or Keefe's weird genetic stuff?
- (261) Keefe has a photographic memory and the parallels between him and Sophie are established soooo early
- Not Dex calling his mom's ability useless (285)
- What is the purpose of having fancy star people (Sir Astin) if they're not allowed to know Elementine, which is, like, the only relevant star?
- (308) Sophie must be extremely good at sandcastles to make an "exact replica" of Eternalia
- (324) hindsight is 20/20; Tiergan is over here telling Sophie that no one "got rid of her" and that she's special like it isn't the most obvious thing in the world that he's Black Swan
-(355) is Alvar claiming Alden is crazy with the fire theories because he's Neverseen and doesn't want Alden to keep investigating?
- (366) Okay, so a messenger delivers the adoption cancellation scroll ... I would assume that for messengers to deliver mail, they need access to all houses in the Lost Cities ... so if I was in the Neverseen, I'd just be a mail person, cause then you get free access to everyone's houses...
- (409) I want to see more Mesmer stuff ... like give me the implications
- (420) do we know exactly who the kidnappers are? Like which of the Neverseen kidnapped Sophie? Because someone shows hesitance about hurting Dex (I looked it up: it's supposedly Gethen, Brant, Trix, and Alvar)
- (445) First of all, Sophie could've easily done a Quick Look at the identities of the Neverseen here, and secondly... which Neverseen member is fat?
- (459) does the Neverseen have a hydrokinetic that they were able to create a tidal wave?