What is the concise book of Fiqh that addresses common jurisprudential questions among youth, and presents the most authoritative rulings without delving into the various schools of thought, so that it may be easily accessible to young people returning to Allah?

We have clarified what a beginner student of knowledge should study in Fatwa no. 65639. We do not know of a specific jurisprudential book that possesses the characteristics you mentioned, but the book "Masail At-Ta'leem" by Shaykh Bafadhal is useful and easy. One can also benefit from websites such as Al-Murabbi website by Shaykh Muhammad Al-Duwaish and Rasid website, which focus on youth issues and their questions.