This is indeed an interesting question, especially in regards to the famous book Kitab Sulaym ibn Qays al-Hilali.
There is no doubt regarding the authenticity, nobility and reliability of Sulaym ibn Qays al-Hilali.
In regards to the narrator Aban ibn Abi 'Ayyash, there are rijali scholars who weaken him, and also classify him as a fabricator or a liar.
However, as far as the book is concerned, as some scholars like Ayatullah Milani say, its chain is not solely from Aban ibn Abi 'Ayyash.
Seyyid al-Milani says there are multiple chains to the book.
As you know, like other cases in our Shi'a heritage, there is no unanimous view regarding this. There are also a few editions of this book as well. One is a 3 volume edition, researched and edited by Ayatullah Muhammad Baqir al-Ansari al-Zanjani. In this edition, volume one has been dedicated to researching all the views regarding the book and the narrators of the as well. It is worth the read for those familiar with Arabic.
An interesting article that deals with this book and its narrators, written byAyatullah Badri in his website:
In brief, there are those who completely accept the book, those who completely reject it, and those who say it has a mixture of authentic and weak statements.
Whatever the case may be, it is an interesting book to read, and for those eager to expand on the rijali side of this book, you must engage in the detailed research in this field.
With prayers for your success.