I started to create txt files. There I note noteworthy things - original file format, sometimes whole filename; things I did before final mobi (like losing horizintal line or adding space between paragraphs or centering headings).
Also path I took, for example lit ->epub in C, tweak html ->prc in MC.
And things that irritated me while reading - missing toc, missing <p>-s (results in whole dialog being in one paragraph), typos. Did I correct them and where (like, if I grab html from epub, make prc, during reading find some things to improve. I twiddle with html-s that Mobi Creator is using, make new prc and continue reading it. Epub stays unchanged.)
Things I tried to do but was unsuccessful, things I maybe could do before next reading (space between chapters, color the headings ...)
My final quality rating concerns only mobi/prc file, but if in the future I aquire need for epubs and conversion from mobi does not work out, it's easy to see what I changed and do it for epub.
Txt opens very fast, so it's just one click to see why rating is '3' for example.