[mapozyan]

Hi Uncle Robin and thanks for your feedback.

First of all, I suspect that after reinstalling Calibre you got some new library ID which actually has GUID format.

You can take closer look at your caps.json file that you will find in %APPDATA%\calibre\plugins folder.

For me it looks like this:

{
  "autoindex": false,
  "concurrency": 5,
  "e5b4b71b-b652-498e-91b8-9b7235d4b734": {
    "index_state": {
      "1013:RAR": {
        "__class__": "datetime.datetime",
        "__value__": "2020-06-07T22:37:09.753607+00:00"
      },
      "1014:RAR": {
        "__class__": "datetime.datetime",
        "__value__": "2020-06-07T22:37:09.981606+00:00"
      },
.............................................
}

So for me my library ID is e5b4b71b-b652-498e-91b8-9b7235d4b734.

Once you reinstall Calibre you will presumably get another ID and this will trigger full reindex.

But why it would reindex all your books again I have no clue yet.

What you can try is to make a backup of your caps.json file, then add another book and finally compare new json file with previous one. This will give you a good hint on what is going.