A little research reveals that each of the given books or series was written by an author whose name contains two initials. The given numbers can be used to index into the abbreviated first and middle names to give letters:
| C. S. Adler | Carole (2) | Schwerdtfeger (4) | A | W |
| S. E. Hinton | Susan (5) | Eloise (4) | N | I |
| C. S. Lewis | Clive (3) | Staples (2) | I | T |
| J. M. Barrie | James (3) | Matthew (5) | M | H |
| R. M. Ballantyne | Robert (2) | Michael (5) | O | A |
| R. L. Stine | Robert (1) | Lawrence (1) | R | L |
| P. G. Wodehouse | Pelham (1) | Grenville (6) | P | I |
| T. A. Barron | Thomas (2) | Archibald (3) | H | C |
| T. S. Eliot | Thomas (6) | Stearns (3) | S | E |
The letters from the first names spell out ANIMORPHS, and the middle names give WITH ALICE. The author of the Animorphs series is K. A. Applegate. Since the K. A. stands for Katherine Alice, the answer is KATHERINE.