I did deep dive the LibrarianSync module/software... That software does NOT work anymore... And probably will not work without some big change... See
this entry.
Technically, as far as I understand, one way to be able to access the involved databases was to use
Code:
http://localhost:9101/change
(see
wiki section Collections).
Amazon decided that it was not their policy
(their policy seems to be: make money, only make money... do NOT consider customer desiderata that was NOT planned in their business plan and implement their plan even if it breaks a nice hack... close any open gate that could let a hacker change the customer expectation... In fact they act as if they had a monopoly not considering that other companies do provide similar product that CAN be hacked/improved/tuned...)
Again, as far as I understand, the database is undergoing changes and LibrarianSync would have come in their way, so they were
obliged to brake it
(poor developpers hit by hacks... Luckily, for me, they are not developping linux; unluckily, for us, they are not from Microsoft who would have bought the technology... sight).
Note that I could NOT find anymore the reference documents used by those who did develop the LibrarianSync hack.
I do see a way to
repair 
the LibrarianSync, but it would be a big work for me and I feel that it will be invalidated as soon as I publish it, so I just use my kindle till it dies while looking around for a better alternative...
Anyway I share the frustration. I doubt that I will buy Amazon kindle or even Amazon products anymore. I would give my kindle a 3 out of 10 in any
Net Promoter Score survey and
such a high result would be only for the quality of the harware...