Grabbed this for my six-year-old after reading one of the Library of Doom books, liking the fact that the Return to the Library of Doom books were a bit longer. She read it in two settings instead of one, like the other one. Perfect for reluctant readers. It's an early chapter book and is chock full of beautiful illustrations and effects around the words (which my daughter loved most of all).
Adam wants to buy his mother a book for her birthday, and he finds the perfect one, a book about monsters. Trouble is, he has to get to the library to buy it, and that night, there's a lightning storm. Despite knowing he shouldn't, Adam decides to ride his bike across town, where the lightning has had some interesting side effects.
The story is really well paced and engaging, packed full of action. I like the discussion questions and writing prompts at the end, which were something fun to do afterwards. The ending itself, though, was a bit disappointed. It was a fine ending, but it felt almost incomplete in a way, and my daughter wasn't a big fan of the open-ended conclusion. All in all, still a good read, and would definitely recommend the series.