You see these books? Do not rec these books to me. Not on the grounds of "diversity!!!" or any other reason.
Dragon riders in a fantasy setting based on ancient Egyptian culture. This should be an easy sell. But while technically all the characters are POC, they're the Hollywood version of ancient Egypt: ambiguously brown at best, as you can tell by the covers, and ambiguously white at work. Definitely not Black.
Of the two warring kingdoms, the one whose people have darker skin are presented at first as the enemy; vicious, cruel, conquering. The "good" guys are lighter, and I don't think we actually get confirmation that they're brown-skinned at all, since there are multiple instances of those characters described as being pale or as going "white with shock."
Aside from that, it's disgustingly misogynistic, and the narrative explicitly supports it. Female characters (of which there are few) are constantly being made the standard for weakness and foolishness, even when they're achieving just as much as or more than the guys. The only time a female character is given any praise is when she's deliberately being divorced from femininity, because she's "not like other girls." Oh no, she's smart, and brave, and strong, just like any of the boys.
In fact, misogyny practically becomes a plot point. In the second book, a group of young men are selected and trained to become dragon riders, and these characters are shown in the most admirable light. Although they're allowed to have some minor faults, in the course of raising their dragons they mature and become brave, devoted, loyal, generous heroes.
In the fourth book, the lone girl among them- our Strong (and in the narrative's eyes, irritatingly) Female Character- forms her own all-girl group of dragon riders, just to prove she can. While not completely condemned by the end of the book, it's still treated as a mistake. Because, you see, girls make terrible dragon riders. They're vain, lazy, catty, bitchy, and they care way too much about boys. They're not devoted to their dragons the way the boys are; they don't become each others' faithful comrades-in-arms. And feeding baby dragons raw meat? Sooooo icky! Girls can't handle blood and guts!
Also? It's homophobic. There is one gay character (he's Greek). And he is a Magical Queer. He is the Gay Best Friend (although he isn't effeminate, because this narrative can't even handle girls being feminine, let alone guys). He has no storyline and barely any personality of his own other than being conveniently around to Deus Ex Machina whatever the plot calls for with his weakly-written magic. This guy's not even a native to their country and risks his life to help their war and rebellion for zero gain. His sexuality is just a joke.
And on top of all that? It is not well-written. There's no sense of voice; the characters are more or less interchangeable; the protagonist is unlikable but not presented as such, and he's Never Wrong; the sentences are often poorly crafted, and overall the whole thing has a bland tone.
So don't come to me using these books as a "racism is over!" gotcha. It just shows me that you really haven't thought this through.