For those who don't already know: Squirrel Girl has a tail like a Squirrel (but human sized) that she stuffs into her pants to pass as "normal", she can talk to squirrels, and she has the proportional strength of a squirrel. Squirrel Girl, while super strong, always tries to use her wit and intelligence before resorting to an actual fight.
Doreen Green is just trying to navigate middle school as a normal kid while her super-hero persona, Squirrel Girl is so-popular the other students have set up a fan club that goes out on patrols to try to see Squirrel Girl in action. Everyone is excited about a new mall opening near town, but before the mall opens, Squirrel Girl needs to deal with LASER LADY.
Bonus: There's a sub-plot here that feels like a nod to Jason Reynolds' book Miles Morales: Spider-Man, while taking the story in a very different direction. This may not have been on purpose, but I like to think that it was.
In case it isn't clear, I highly recommend this book. I also suggest picking up the first book, but there's no references to the first book that are not explained in this second book.