Crescent Dawn is the twenty-first Dirk Pitt book. Ostensibly, per the webpage and cover, it’s by Clive Cussler with his son Dirk Cussler (not sure who was named after whom), but given that SYKM says that Clive Cussler died in 2020, and that the last few books were already co-written, it seems it really must have been written by just the son ???
In any case, it’s on sale in the US for $0.99 right now.
Devil’s Gate is the ninth Dirk Pitt/NUMA files book. It’s $0.99 right now in the US.
Kindle US: https://www.amazon.com/dp/B0CNVXTYX5
Kobo US: https://www.kobo.com/us/en/ebook/devil-s-gate-14