Choose your own book with a Monster Theme.
Here is an example of what one club member read:

"Monster and Boy" by Hannah Barnaby

When Monster (who lives under the bed) meets Boy (who sleeps in the bed), Boy starts to scream―and Monster promptly swallows him. It's the beginning of a beautiful friendship!

Told with a warm, cozy voice, the story is brought to life with adorable two-color illustrations. Filled with adventure and humor, this chapter book is perfect for sharing with kids just aging out of picture books and for newly independent readers.

Fall in love with the friendship between Monster and Boy in this exciting new chapter book series from writer Hannah Barnaby and illustrator Anoosha Syed.

Description from amazon.com book's page.

Choose your own book with a Superhero Theme.
Here is an example of what one club member read:

"Mia Mayhem: Is A Superhero!" by Kara West

Mia Macarooney is a regular eight-year-old girl who finds out that she’s A SUPERHERO! Her life literally goes from totally ordinary to totally super when she’s invited to attend the afterschool Program for In-Training Superheroes a.k.a. THE PITS! And the crazy thing is, in a weird meant-to-be sort of way, all of this news somehow feels super right. Because all her life, Mia thought she was just super klutz...but it turns out, she’s just SUPER! So now, it’s up to Mia to balance her regular everyday life and maintain her secret identity as she learns how to be the world’s newest superhero!

With easy-to-read language and illustrations on almost every page, the Mia Mayhem chapter books are perfect for emerging readers. Description from amazon.com book's page.

The first day Georges (the S is silent) moves into a new Brooklyn apartment, he sees a sign taped to a door in the basement: SPY CLUB MEETING—TODAY!
 
That’s how he meets his twelve-year-old neigh­bor Safer. He and Georges quickly become allies—and fellow spies. Their assignment? Tracking the mysterious Mr. X, who lives in the apartment upstairs. But as Safer’s requests become more and more demanding, Georges starts to wonder: how far is too far to go for your only friend? Description from amazon.com book's page.