Moone Boy: the Blunder Years by Chris O'Dowd and Nick V. Murphy
"Martin Moone is eleven and completely fed up with being the only boy in a family of girls. He's desperate for a decent wingman to help him navigate his idiotic life. So when best mate Padraic suggests martin get an imaginary friend--or "IF" for short--he decides to give it a go. His first attempt is Loopy Lou, a hyperactive goofball who loves writing rubbish rap songs.But Martin soon gets fed up with Lou's loopiness and decides to trade in his IF for someone a little less wacky. Enter Sean "Caution" Murphy, an imaginary office clerk in a bad suit with a passion for laziness and a head full of dodgy jokes. Sean is full of tips and tricks to guide Martin through the perils of the playground, from dealing with his sister's pranks to besting the Bonner boys. But getting rid of Lou is not that easy, and having TWO imaginary friends is a recipe for trouble!"
The Friendship Riddle by Megan Frazer Blakemore
How Lunchbox Jones Saved Me From Robots, Traitors, and Missy the Cruel by Jennifer Brown
Get Real: What Kind of World are YOU Buying? by Mara Rockliff
The Book of Dares for Lost Friends by Jane Kelley
Dr. Critchlore's School for Minions by Sheila Grau