I've read foundation and end of eternity, loved both, but never read one of robot books! I don't know why ... maybe I don't know where to start or something, and so it just slipped out my reading.
I highly recommend them. They’re set in the same world as foundation but are crime novels focusing around a detective from earth and dealing with an increasing cultural differences between planets and issues of artificial intelligence and robots that pass for human. One of the things I love is how Earth is in many ways the most foreign planet to the reader.
Start with The Caves of Steel, then The Naked Sun, followed by The Robots of Dawn, and finally Robots and Empire which ties the setting into Foundation
I found a few orders to read the books in on Reddit and chose to go with the chronological order. I’m currently on foundation and so far its worked pretty well. There were a few other orders that had their own benefits so might be worth a duck duck go. But here is the chronological order: