I've been trying to remember the name of a book I read in the mid to late nineties. All I can remember is the author had a forward where he spoke about mental illness, specifically bi-polar, I believe, and how it would have been to live with mental illness with no treatment back in the mid 1800's(I believe the novel took place in the late 1850's/60's). The only other thing I remember is the main protagonist had a cap and ball gun, the Walker Revolver I think. Not much to go by but it's been bugging the heck out of me that I can't remember it. Thanks for any help.