Once again, I perhaps gave too much of the game away.
This is Goosebumps #28: The Cuckoo Clock of Doom
Our protagonist Michael always gets in trouble for stuff his bratty younger sister Tara does. After his 12th birthday, Michael's father brings home an antique cuckoo clock. Later in the night, Michael damages the cuckoo bird, planning to frame Tara. This instead causes time for Michael to flow backwards. Eventually, he has to fix the problem before he ceases to exist. This book's twist ending is probably the most iconic in the series.
©Scholastic/RL Stine