القواعد و الأصول الجامعة و الفروق و التقاسم البديعة النافعة
للشيخ عبد الرحمن بن ناصر السعدي
"The rules, the general bases, the distinctions and the original and beneficial subdivisions" by Shaykh As-Sa'di, is an excellent work - here in its best edition - which is divided into two parts:
In this first part, Shaykh As-Sa'di explains 60 rules and principles in fiqh and in religion in general.
In the second one, he quotes real and false differences that there are in similar fiqh questions and the subdivisions relating to these questions.