I'll always recommend Michael Pierce's Motes and Beams and Dario Nardi's Neuroscience of Personality. Michael Pierce is a MBTI Youtuber, but he's also in the process of getting a graduate degree in philosophy, which informs a lot of his understanding of type, while Dario Nardi performed brain scans on people of various types.

Michael Pierce's Motes and Beams and Dario Nardi's Neuroscience of Personality.