Fingers : a piano exercise book / by Ana Sorina Popa, DMA; illustrations by Ana Sorina Popa, with Lauren Anhalt and Jennifer Bradford; editor Mary Eilliff.

Enhanced descriptions from Syndetics:

Fingers is a book of exercises that focus piano playing on finger and hand coordination, using off-staff notation and finger numbers. The fruit of two decades of pedagogical experience, this book teaches in an organized and graded way the fundamental elements of piano technique, taking the young beginner from the first encounter with the keyboard to playing a C Major scale. You will find exercises that teach finger independence, parallel and contrary motion playing, legato and staccato, piano and forte, and a wealth of practice suggestions.

The absence of conventional notation is intentional. The beginning of piano study is full of applications
of information that require young students to make multiple conceptual and physical jumps. Since the best learning strategy is to first separate, practice, and absorb each element and then combine it with the rest, the exercises in this book focus on finger sequencing while using elements that are already familiar to young beginners - colors, numbers, and letters, therefore eliminating the need to combine music reading with intricate finger patterns prematurely.

Apart from where specific notes are indicated, the rest of this material can be played on any keys.

Fingers can be learned as a supplement to a conventional piano method or in preparation to the first piano lesson. Depending on the approach and time dedicated to each exercise, this material can be absorbed in three to nine months. These exercises are appropriate for ages 4 and older.