Thanks so much for the help chrisridd.

It's nice to know someone took time to read my long post and try to help!
Update to first post:
It's been days since this first happened, and with so many things I didn't understand it's taken me hours and days to even halfway figure it out.
First, I now know that Reader for Mac does indeed take the place of Reader Library and that you can use a Sony reader with it, not just computers and phones.
Second, I finally got my reader to show up in it, and when it does show up, I can sync or not sync as I choose. I don't know why my reader wouldn't show up at first, I think there is something kooky about the Reader for Mac program. Maybe it's just on my computer, maybe it's on all of them, I don't know, but it's kooky.
Third, I took chrisridd's great advice and found the location of my books. Or rather, some of my books. They were in the main library under "preferences" of all places, and then under "Sony Corp". I don't know why my search feature wouldn't show them.
However, finding them and searching into it more, I've discovered that the Reader software syncing has somehow erased most of my books!

When I first posted, it had just happened that after syncing, all the books I tried to open on Reader Library were erased ones, while all the books I tried to open on Reader for Mac happened to be ones that weren't erased (remember, all my titles still show up on both programs as if all my books are still there). That's what led to my confusion while posting in that regard.
I have looked all over my computer and can't find the deleted books anywhere. I've used the search function, the spotlight function and manually searched about everything. I even searched the trash and though apparently deleted, they didn't go there.
I have no idea the rhyme or reason for which books it kept and which it deleted. The ones kept are not all Sony store purchases, and there were some Sony store purchases that were deleted. It included random books in alphabetical order, random books in size order; it just seemed to do it at random. I calculated it and it deleted 49.2% of my books. I wonder if there's something in it deleting very close to half of my library, but I still have no idea how it decided which books to delete.
The problem is not so much that they are deleted. I think I can get most of them, if not all, back, either from the store of purchase if I log in and re-download it (I think) or free downloads such as from the mobileread library.
The problem is that I'm a voracious note-taker and it seems to have also deleted all my notes for those books. Of course I don't take so many on every book, but unfortunately it decided to keep books such as "Breaking Dawn" and "The Princess Bride" where I didn't take many notes and deleted books such as "Love in the Time of Cholera" and "A Room with a View" where I took quite a few. But there is no pattern. It did delete some books that I didn't take any notes in and kept some that I took many notes in. Anyway, having many notes deleted by the software is a big blow and very, very annoying and saddening.
If any of you are going to offer me advice on how to save notes separately, uh, too late!

I've already now learned that it's possible and not even that hard from my days of research these last few days. But unfortunately I never knew about it before or thought vaguely of it being something very hard and complicated, so no notes were saved in separate files before through my own doing. The saddest part is that I was literally very close to start figuring out how to save them separately anyway. That's sort of how I found the Reader for Mac program in the first place, as I was starting to look around and try to figure out some more stuff about my reader (saving and safe-guarding my notes separately being at near the top of the list). Then I pretty much immediately found Reader for Mac and downloaded it and the rest is history. How ironic that so many notes taken over a few years get deleted at the very moment I'm trying to figure out how to save and safeguard them. I think I'll go listen to Alanis Morissette's Ironic for awhile.
What I would still love help with (and
for the TLDR crowd, the main points of this post):
-Now that I have a choice, I'm inclined to use the Reader for Mac software instead of Reader Library, for one huge reason - Reader Library is extremely slow and laggy for me and Reader for Mac isn't.
Does anyone have any tips on making Reader Library not slow or laggy? If that could be fixed I'd just use it.
-But unless that's fixed, I'm using Reader for Mac and I am still having many problems with it. First and most importantly -
whenever I open it a box pops up within minute that says
Quote:
Unable to synchronize the device. Please take a note of the error and contact Sony customer support.
Error: Maximum number of creates at any one time exceeded - error code: -40338 (400).
|
This doesn't happen when the reader is plugged in; it's when the reader is NOT plugged in or connected at all. I press "OK", it comes back within a minute or so, I press the little red X and it comes back within a minute or so, although after a few times it usually stops, but it's very annoying and makes me worried the software is corrupt or something. And it does it every single time I open the program.
Does anyone have any idea what's going on or how to fix this?
-
The Reader for Mac window takes up space from the top of my screen to the very bottom and it won't resize any smaller height-wise. It will let me change its width but not its height. It's annoying because I keep a dock at the bottom of the screen and the dock covers the bottom Reader for Mac controls, so every time I open it I must hide my dock to use Reader for Mac.
Does anyone know how to fix this?
-
Does anyone understand or have any idea why syncing Reader Library with Reader for Mac deleted half my books and notes?
-This is a last-ditch effort but
does anyone have any suggestions or ideas about how to possibly recover or find the lost/deleted books and notes that the program deleted? I'm guessing they're probably gone for good, but if I can somehow find them or recover them, that'd be incredible.

so much for any help!