999 Bức thư gửi cho bản thân is an Android application developed by cheuhyakuroku that allows users to read the bilingual Vietnamese - Chinese book "999 Letters to Myself" conveniently. The book includes both simplified and traditional Chinese, making it easier for newcomers to improve their Chinese reading skills. The application is especially handy for those who don't want to carry around a thick book.

The book is about overcoming difficulties that are beyond our imagination, and how we can remain happy and confident despite the pain of the past. With this app, users can enjoy reading the book in a more accessible way, helping them to learn and grow.