Not a history book, per se, but a great tour into the culture and philosophy of Unix: The Art of Unix Programming [1], by Eric Raymond. Chapter 2 is titled "History."

You also have resources like The Unix Heritage Society [2], who show a timeline of historic events on their wiki [3].

I bought Brian Kernighan's memoir [4], which so far is an incredibly detailed and personal account of his time at BTL.

[1] http://catb.org/~esr/writings/taoup/html/

[2] https://www.tuhs.org/

[3] https://wiki.tuhs.org/doku.php?id=events:start

[4] https://www.amazon.com/UNIX-History-Memoir-Brian-Kernighan/d...