I really thought this book was beautifully written.
Ptolemy Grey is a 91 year old black man living in Los Angeles and suffering with dementia. His primary caretaker has been killed in a drive by, and other relatives have popped up to get him to the funeral. There he meets a ward of his great/grand-niece who actually sees him for the man he was, and values him as he should be.
In all of this, a doctor has made an unethical offer - let Ptolemy try an illegal experimental drug. He will be lucid for a few days or weeks, but the drug will most likely kill him. It has definite shades of Faust.
I generally don't like it when authors write in dialects, but it works really well in this story and Mosley is a genius at writing conversations. More than the dialect, the word choices tell a great deal about the the characters speaking. The descriptions of Ptolemy's dementia, mental slips, and living conditions (as an elderly person living alone) are heart breaking and really well written, as are his memories of growing up and living in the Jim Crow South.