This is how I work on my book. Part1
It starts, when I loose a game in 30 moves or less. I don’t look at all my games,
but sometimes I find a fast loss. I always use "show evaluation", so I know when
my book ends, and if it was my book error or an engine play. If I think my position
from the book was bad - I am changing my book. First I check if I have stronger
alternate move in my book earlier. If I do - I disable loosing continuation.
If I don’t - I will add some new moves. Adding new moves will create some variety,
and it may create better position than before.
One of the games in the B81 list (updated 10 Dec 2004) on the beginning says
"analyzed", you can see my analysis in that line. When I analyze game I start
from the end of the game. Maybe not exactly the mate, but when one side has big
advantage like +3 or -3 or more. Then I go back from that position, too see
other moves, which are recommended by engine for the loosing side. I make those
other recommended moves and make a few moves to see if the lost side is still
lost. If not, I add the better moves to my book. If loosing side has difficulties
in many lines, it may be a new "killer line" :).