Solo: A Star Wars Story has several interesting details. For example, it delves into Han Solo's backstory, like how he got his name and his early adventures. One major spoiler is that we learn about his relationship with Qi'ra and how she's involved with the criminal underworld. The movie also shows how he meets Chewbacca and the origin of their friendship.
Well, one big spoiler is a surprise romance development that you wouldn't expect. Also, there's a crucial decision made by a supporting character that has huge consequences. But it's better to discover these yourself while reading.
One spoiler that might surprise some is the appearance of Darth Maul at the end. It connects the story to the larger Star Wars underworld and hints at future events and conflicts that could involve Han Solo and his crew, though this was a bit of a surprise cameo for many viewers.
I can't reveal too many spoilers, but let's just say there are some major plot twists involving the protagonist's rise to power and unexpected alliances.
I'm not familiar with this novel specifically, so I can't say for sure who the main characters are. But usually in a story about a cursed king, the king himself would be a main character.
One of the most notable details in 'Solo' is the look and feel of the different planets. Corellia is shown as a gritty, industrial world. As for spoilers, Han's encounter with Beckett and his crew is a big part of the story. Beckett is initially Han's mentor but things change as the story progresses. It's also a spoiler that Han has to make some tough moral choices during his adventures.
I'm not sure specifically as I haven't read it. But generally, it might be about a romantic relationship between a human and a werewolf king who is cursed. It could involve the challenges they face due to his curse and the werewolf nature, like dealing with his transformation, the werewolf pack's reaction, and how their love overcomes all these obstacles.