As you might know, in addition to Bhagavad Gita, there are 60 other Gitas spread across various scriptures. Like Vyadha Gita, Awadhoot Gita, Ribhu Gita, Ishwar Gita, Ashtavakra Gita etc.
While Bhagavad Gita gives summary of various paths for spiritual progress, ‘most of these other Gitas’ focuses on one or few paths and go extreme deep in them. Due to the depth, these other Gitas are not very famous with general public, but they are very well known for the followers for the specific paths.
One of my favorites, Ashtavakra Gita specializes on Dnyan/Jnana Marg, and it is a dialogue between King Janaka and Rishi Ashtavakra, hence name ‘Ashtavakra Gita’.
Just to give a glimpse of the difference in depth between Bhagavad Gita and Ashtavakra Gita. For Dnyan Marg, Bhagavad Gita, gives outline of the path, attributes of the followers, along with showing how Krishna is the final destination.
Ashtavakra Gita, on the other hand, take one on the Dnyan Marg ride, makes you reach the destination, helps you settle there, in such a way that you will never come back. Personally, for me, it has been an insane experience. Each time one reads it, newer deeper levels are reached.
Having said that, it does not mean we leave Bhagavad Gita, and go reading these other Gitas. Correct approach is read Bhagavad Gita, find that one path which suits you, and then read other Gita, Upanishads ‘specific to your path’. This will get you where you want to reach.