Worser / by Jennifer Ziegler.

Enhanced descriptions from Syndetics:

A bullied 12-year-old boy must find a new normal after his mother has a stroke and his life is turned upside down.
William Wyatt Orser, a socially awkward middle schooler, is a wordsmith who, much to his annoyance, acquired the ironically ungrammatical nickname of "Worser" so long ago that few people at school know to call him anything else.

Worser grew up with his mom, a professor of rhetoric and an introvert just like him, in a comfortable routine that involved reading aloud in the evenings, criticizing the grammar of others, ignoring the shabby mess of their house, and suffering the bare minimum of social interactions with others. But recently all that has changed. His mom had a stroke that left her nonverbal, and his Aunt Iris has moved in with her cats, art projects, loud music, and even louder clothes. Home for Worser is no longer a refuge from the unsympathetic world at school that it has been all his life.

Feeling lost, lonely, and overwhelmed, Worser searches for a new sanctuary and ends up finding the Literary Club--a group of kids from school who share his love of words and meet in a used bookstore- something he never dreamed existed outside of his home. Even more surprising to Worser is that the key to making friends is sharing the thing he holds dearest- his Masterwork, the epic word notebook that he has been adding entries to for years.

But relationships can be precarious, and it is up to Worser to turn the page in his own story to make something that endures so that he is no longer seen as Worser and earns a new nickname, Worder.