This is the collection I've built for grades K-2. Depending on the reading level of the children, the books can be read alone, read together, or read aloud.
Amanda Pig by Jean Van Leeuwen
Amelia Bedelia by Peggy Parish
Arthur by Lillian Hoban
Diary Books (Worm, Spider…) by Doreen Cronin and Harry Bliss
Frances books by Russell Hoban
FranklinFrog and Toad by Arnold Lobel
George and Martha by James Marshall
Henry & Mudge by Cynthia Rylant
Horrible Harry by Suzy Kline
Little Bear by Else Holmelund Minarik
Nate the Great by Marjorie Weinman Sharmat
Paddington by Michael Bond
Poppleton by Cynthia Rylant
Do you have other favorites that didn't make our list?