“The Third Mushroom” by Jennifer L. Holm is the perfect sequel to “The Fourteenth Goldfish.” In this book, Ellie is in middle school and has a best friend, Raj. When her grandfather, Melvin, comes to stay with them in the body of a fourteen year old (that’s what happens in the first book), things get interesting.

Melvin attends middle school with Ellie, and she’s excited because now she can enter the science fair with her grandfather, who is a world-renowned scientist with two PhDs (as he keeps reminding everyone). Melvin had gotten an unusual jellyfish delivered to the house (it was a formula from a rare jellyfish that caused Melvin’s age regression). It turned out, when they unpack it, that it’s an axolotl, a type of salamander that lives underwater and has gills. The axolotl is unusual because it can regrow body parts.

They decide to experiment with the axolotl for the science experiment, but when Melvin uses himself as a subject (after beginning with wingless fruit flies that surprisingly grow wings), things get strange.

Holm writes about science in a manner that will have readers wanting to do their own cool experiments. But even more than that, she writes about problems that middle school kids, and older grade school kids, and even high school kids might have. For example, when Ellie and her best friend Raj go on a date, it doesn’t work out the way they think it will.

Ellie also manages to reconnect with a friend she had stopped being friends with, and Holm shows readers that there can be different kinds of friends. Holm is talented at creating characters who are multi-dimensional. While Melvin is cantankerous, he has a soft side, and Holm takes readers through his comforting Ellie when she experiences loss.

The ending is fabulous and feel-good and will make readers smile. Loose ends are tied up, Ellie has learned and grown in the story, and Melvin gets a perfect ending. Readers learn that sometimes you need to keep trying things, even if you don’t like them at first, because that’s how life is. Don’t get stuck in a rut. The readers even learn the truth that it’s dangerous for cats to go outside on their own.

One caveat is that both books, “The Fourteenth Goldfish” and this one should be read together. This book won’t make quite as much sense if it’s read as a stand alone, although it would still be very enjoyable.

Please note: This review is based on the final, hardcover book provided by the publisher, Random House Books for Young Readers, for review purposes.