You should really start at book 1, there are three 5 book series’s, only one of which explains the scorching in detail and why it happened (this happens in the newest book). The first series is dragonets ending the Sandwing War of succession. Basically, humans killed the former queen and their daughters disagreed on who should be queen. Then they forced all of the other tribes into it, but here’s the rundown:
Blister: smart but pretty evil, allied herself with the Seawings and the Nightwings wanted to use her to get help taking over Rainwing territory.
Burn: an absolute psychopath, allied herself with the Skywings because Scarlet was somewhat of a friend (and also a psychopath) and the mudwings also allied with her out of fear.
Blaze: the opposite if those two, and pretty incompetent. She was willing to give the Icewings a ton of land if they helped her, obviously they jumped in for it since it was a lot of territory they wanted.