In Trouble, mermaids Shelly and Echo are excited for their school year at Trident Academy, but an argument and an intrusive classmate test their friendship. In Battle, Echo is invited to Pearl's birthday party but Shelly isn't; she must decide how best to handle the situation. While the dialogue in these first series installments falls flat, the black-and-white illustrations are charming. Glos.

Prolific Dadey's (Keyholders: The Wrong Side of Magic, 2010, etc.) latest series follows young mermaids through turbulent friendships. Eight-year-old best friends Shelly and Echo are overjoyed to be starting school at the prestigious Trident Academy at the same time. Rambunctious and good-natured, together they cause mild trouble, especially in trying to find a way to make grumpy Mr. Fangtooth crack a smile. Their friendship wobbles when they disagree over whether to ask Shelly's grandfather for help on a school project or not. The minor tiff leads to Echo's sudden friendship with Pearl, a rich snob who dislikes Shelly most of all. Echo and Shelly miss each other, though, and restore their friendship while reaching out to another mermaid who is new to the area and has made friends. While Echo and Shelly are not particularly distinctive, and Pearl and the archetypal token boy, Rocky, are cartoony, the characters' interactions are funny and believable. The friendship-driven conflicts continue in Battle of the Best Friends (publishing simultaneously). In Battle, Pearl books a top under-the-sea band to perform and invites Echo but not Shelly; the end again reinforces the importance of inclusiveness and rewards those who are nice. The underwater setting adds some dimension to straightforward friendship stories. (class reports written by each character, song lyrics, author's note, glossary) (Fantasy. 6-9)