Mockingbird was fantastic. Can't recommend it enough. I learned so much -- not only about what went into writing Mockingbird, but also about the pivotal (and uncredited) role she had in the writing of In Cold Blood. I knew she went with Capote to Kansas to assist with research, but had no idea how large a role she played in cultivating the key relationships he was incapable of developing on his own -- relationships that would give them access to first-hand information from investigators. Capote was such a shitbird.
All of the insights into Lee -- her tenacity, stubbornness, rugged individuality, humor, complications -- just made me admire her that much more.
As is so painfully typical for me, I actually bought the book the day it came out (in 2006) so that I'd have a first edition -- and just read it now.