Amber Brown goes fourth / Paula Danziger ; illustrated by Tony Ross.

Enhanced descriptions from Syndetics:

Author Paula Danziger loves to write for and about kids, and kids love her! They especially love her feisty and lovable character Amber Brown.
Putnam is pleased to present the third book in the Amber Brown series, Amber Brown Goes Fourth illustrated by Tony Ross), a realistic, poignant portrayal of Amber and her single mom, who are both adjusting to divorce. And like the series, Amber Brown Goes Fourth is highlighted with Danziger's lively, laugh-out-loud, first person narrative.

Amber Brown has conquered third grade with her best friend moving away, and chicken pox in London with her Aunt Pam, but now... fourth grade! Still missing Justin and adjusting to her mom beginning to date, Amber is determined to substitute a new friend at school named Brandi as her new best friend. But Amber finds out that you can't "substitute" a best friend; one has to accept each new friend as they are and let the friendship grow. She wonders how she can keep people who are far away from her -- her dad and Justin -- in her life and whether anything will ever be the same again.

Paula Danziger's appeal is also strong with the young adult crowd as well.
Her titles in this genre include, The Cat Ate My Gymsuit, Remember Me to Harold Square, The Divorce Express, Can You Sue Your Parents for Malpractice? and Thames Doesn't Rhyme with James .