1. Winnie-the-Pooh (1926)
2. The House at Pooh Corner (1928)
3. When We Were Very Young (1924) - This book features poems about Christopher Robin and other characters.
4. Now We Are Six (1927) - This book is also a collection of poems, many of which feature Christopher Robin.
While not all of these books are strictly "Winnie the Pooh" books, they all feature the beloved bear and his friends.