American books that do the “collecting monsters” thing right

I grew up on Pokémon and Digimon and still love that feeling of a world where creatures are partners, tools, or weapons. But most American takes on this end up either being cute kids stuff or trying too hard to be dark and edgy. I want something in between. Where the bond matters but there are real stakes.

I know about the Animorphs series from way back, which had that body horror angle that Pokémon never touched. Also heard about the Rema Chronicles or stuff like that. Not looking for graphic novels necessarily, but I'm open.

What novels capture that energy of training, collecting, or battling with creatures in a way that feels fresh? American authors especially, but anything that isn't just imitating the Japanese formula.