As a revelation that is self-explaining, fully detailed, complete, and with lessons easy-to-learn the Quran should be, according to the Quran itself, the only authority of Islam.
As the Quran itself claims, the Quran explains itself:
11:1 Alif-Lãm-Ra. ˹This is˺a Book whose verses are well perfected and then fully explained. ˹It is˺ from the One ˹Who is˺ All-Wise, All-Aware.
75:19 Then it is surely upon Us to make it clear ˹to you˺.
What is fascinating about the Quran is of a particular topic or account is contained in several related verses that are usually not in one place but scattered throughout the Book. Often one verse is associated with another in such a way that one supplement, explains, clarifies, or throws more light on another. Thus, according to the Quran’s own assertion, the Quran is not only the best hadith (ahsana alhadeethi 39:23) but it is also the best interpreter of itself (ahsana tafseeran 25:33) as it goes on its way clarifying its own messages.
17:41 And We have detailed things in this Quran in various ways so that they may receive admonition, yet it has only added to their aversion.