Salam alaikum.

I remember once during the debate on shia beliefs in Quran, one from them quoted book by Sulaym ibn Qays, as a proof that shia believe in authenticy of present Quran.

Taken from “Kitab ad-duafa” by ibn Ghadaere:

( 1 ) – 1 – سُلَيْمُ بنُ قَيْس، الهِلاليّ، العامِريّ. روى‏ عن أميرالمُؤْمِنين‏(1)، والحَسَنِ، والحُسَيْنِ، وعليِّ بن‏الحُسَيْن(ع). ويُنْسَبُ إليه هذا الكتابُ المَشْهُورُ.(2) وكانَ أصحابُنا يقُولُون: إِنّ سُلَيْماً لا يُعْرَفُ، ولا ذُكِرَ في خَبَرٍ. وقد وجدتُ ذِكْرَهُ في مواضعَ من غير جِهَةِ كتابِهِ، ولا من روايةِ أَبان ابن أبي عيّاش عنهُ.(3) وقد ذَكَرَ لهُ ابنُ عُقْدة في «رجال أمير المؤمنين (ع)» أحاديثَ عنهُ. والكتابُ موضُوعٌ، لا مِرْيَةَ فيهِ، وعلى ذلك علاماتٌ فيهِ تَدُلُّ على ما ذكرناهُ. منها: ما ذَكَرَ أَنَّ مُحَمَّدَ بنَ أبي بَكْرٍ وَعَظَ أباهُ عندَ مَوْتِهِ. ومنها: أَنَّ الأئمّةَ ثلاثةَ عَشَر. وغيرُ ذلك.(4) وأسانيدُ هذا الكتابِ تختلفُ: تارةً بِرواية عُمَر بن أُذَيْنة، عن إبْراهيم بن عُمَر الصَنْعانيّ، عن أبان بن أبي عيّاش، عن سُلَيْم. وتارةً يُرْوى‏ عن عُمَر، عن أبانٍ، بلا واسِطةٍ.(5)

1 – Sulaym b. Qays. Al-Hilali. Al-`Amiri. Narrated from Amir al-Mu’mineen (as), al-Hasan (as), al-Husayn (as) and `Ali b. al-Husayn (as). This famous book is attributed to him. Our companions would would say that Sulaym is not known, and not mentioned in (any) report. I have found mention of him in places other than from the direction of his book, and not from the narration of Aban b. Abi `Ayyash from him. Ibn `Uqda has made mentioned hadiths from him in ‘Rijal Amir al-Mu’mineen.’ The book (attributed to Sulaym) is a forgery, no doubt about it. There is evidence showing what we have mentioned about it. From it: what it mentions about Muhammad b. Abu Bakr exhorted his father at his death. And for it: that the Imams are thirteen. And other than that. The isnads of this book vary. Sometimes by the narration of `Umar b. Udhayna from Ibrahim b. `Umar as-San`ani from Aban b. Abi `Ayyash from Sulaym. And sometimes it is narrated from `Umar from Aban without an intermediary.

Official page of ayatullat Sistani says about ibn Ghadaeere:

وإن ابن الغضائري هو المعتمد في مقام الجرح والتعديل أكثر من النجاشي والشيخ وأمثالهما

…. and ibn al Ghadaeere he is reliable in the matters of praise and critic more than an-Najashi, Shaykh (at-Toose) and (others) like them.