Thanks to all for your suggestions.
Here is my final way of setting things in calibre.
1- In the
Tags, I have created 5 new values from interest
5-Very high to
1-Very low (on top of other tags).
2- As I produce a
catalog book (useful tool, that i tranfer to the device)
3- Opening the catalog and going to the 5-Very high interest to find my most interest first.
I don't know why I haven't though of it myself (thinking that Tags were only reserved for Sci-Fi, Romance, Thriller, Sport or whaterver categories we can think of).
Case solved.