The Musannaf of Ibn Abi Shaybah is one of the well-known compilations of Hadeeth and narrations about the righteous predecessors, in which Ibn Abi Shaybah compiled many Ahaadeeth according to subject, and narrated reports from the predecessors about that subject, regardless of the authenticity of those Ahaadeeth and reports. Therefore, it includes Ahaadeeth classified as Saheeh (sound), Marfoo‘ (attributed to the Prophet), Mawqoof (attributed to the Companions), and Maqtoo‘ (with discontinuity in chain of transmission).
WARNING: The book contains many daif ahadiths and is a go to resource for shiites as it supports their opinion in some cases. However, for ahlus-sunnah, they believe in authentication of the narrations before accepting them and this protects them from misguidance. It is responsibility of researchers and readers to ensure authenticity of narrations before accepting them. Relevant Article: Importance of Identifying the Authenticity of Narrations
Ibn Abi Shayba showed enmity to Abu Hanifa - Allah be well-pleased with him -- as he named one of the longest chapters of his Musannaf "Book of the Refutation of Abu Hanifa" in which he proceeded to list about one hundred and twenty five "Prophetic hadiths which Abu Hanifa contradicted."1 This charge, together with Ibn Abi Shayba's refutation, are refuted in the books of Imam Muhammad Zahid al-Kawthari among others. It remains that the Musannaf is perhaps the most precious mine of information on the juridical positions of the Companions and Successors.
Opinion of the great scholar - Shah Waliullah al-Muhaddith al-Dahlawi:
Shah Waliullah explains various ranks of books of hadith and explain the groups containing 'Mussanafs' as follows:
"The third rank is comprised of those Musnad, Jami’, and Musannaf works compiled before Al-Bukhari and Muslim, during their time, and after them which combine the sound, the good, the weak, and the recognized (ma’ruf) and the uncommon; the anomalous and the objectionable (munkar) the erroneous and the correct; and the continued and the transposed. They do not have the same reputation among the learned scholars, even if they are not given the designation of “absolute rejection”. The learned religious scholars have not given much currency to those hadiths found uniquely in these works, and the hadith scholars have not carried out major investigations into their soundness or faultiness. Among these books are the ones for which no linguist has rendered the service of explaining its rate expressions, nor has any legal scholar worked to reconcile it with the opinions of the pious ancestors, nor has any hadith scholar explained its problematic (mushkil) hadiths nor has any historian made mention of its transmitters. I do not refer to those recent authors who are hair splitters; rather I am speaking of the early leaders (imams) of the hadith scholars.
Therefore their books have remained obscure, unknown, and undistinguished, such as the Musnad of Abu ‘Ali, the Musannaf of ‘Abd al-Razzaq, the Musannaf of Abu Bakr ibn Abi Shaybah, the Musnad of ‘Abd ibn Humayd, Al-Tayalisi, and the books of Al-Bayhaqi, Al-Tahawi and Al-Tabrani. The goal of these authors was to collect whatever they found, not to extract the best, nor to refine them, nor to make them more accessible for use."