Mickey7 by Edward Ashton (well, actually the sequel right now, finished the first book yesterday). I was actually surprised at how good it was given that I haven't heard much buzz around it. Though that might just be me having my head buried in the sand, because apparently there's a movie for it coming out next spring, so it's hardly an unheard of gem lol

But yeah it checked all the boxes for me

• interesting characters with a fair amount of development
• fascinating thought experiments about the nature of consciousness and continuity
• fast paced plot that keeps you on the edge of your seat for most of the book
• interesting aliens and a mysterious planet
• semi hard scifi