They are still books of Hadeeth, usually the 'Ulamaa' refer to them as Kutub Shurooh al-Hadeeth. For details on this topic, you should refer to the very beneficial lecture by Saalih Aal ash-Shaykh called الفرق بين كتب الحديث وكتب الفقه (The Difference Between the Books of Hadeeth and the Books of Fiqh).
------------------------------------------ Abu 'Abdil-'Azeez al-Misree أبو عبد العزيز المصري