I'm going to discuss how I track the books I have ready to read and those that I've read. You may have a different methodology, and if you let me know I'll consider adding your techniques to this page.

• I have a Kindle Paperwhite that I bought in 2016. It has 4GB, it's working just fine, and it's holding over 300 books.
• I also have a free account with BookBub and it tells me of bargain and free ebooks that I can download onto my Paperwhite.
• Getting books for free, legally see the page I created a while ago that's helped me amass more books than I can read anytime soon!

Here's how I handle them all: I've created a Note entry with the info.

• The Note has all books, sorted by author, and in order (if appropriate) under the author.
• Each author grouping has the series (if it's a series) name and the (author) in parens, followed by any notes.
• Each book has the name, and a [h] before the name if I Have it on my Kindle. If no [h] then I may be getting it in the future
• If the book is part of a collection (one file with several books) I change the [h] for each within the collection to [h1] where '1' is the collection number.
• As I am reading the book, I change the [h] to [hr].
• When I finish reading the book, I change the [hr] or [h] to [read]

I use a Note entry because I have several Apple devices and this makes the list of books available on all devices. I'm not sure how this might work on non-Apple devices, let me know!

Sherlock Holmes (Sir Arthur Conan Doyle) British Detective with Watson
1. [read] A Study in Scarlet
2. [hr] The Sign of Four
3. [h] A Scandal in Bohemia
4. [h1] The Red-headed League
5. [h1] A Case of Identity
6. [h2] The Boscombe Valley Mystery
7. [h2] The Five Orange Pips
8. The Man with the Twisted Lip
9. The Adventure of the Blue Carbuncle

So you can see this is a series of books, and the first 9 are listed.
I have the first 7 of the books, I've read the first and I'm reading the 2nd. The 4th and 5th are in a collection as are the 6th and 7th.
I don't yet have copies of the last two books listed.

I may add more books to the list (10, 11, etc) as I read the ones I have or if they become available for free. For example, if BookBub tells me that book 8 or 9 is available for free, I'll download it to my device and add an [h] before it.
This way I can search for author, protagonist (Holmes), or book title, and see its status in my collection.

My colleague CW has suggested a self-hosted application that lets you manage your books. https://github.com/bayang/jelu

From the Jelu site: Self hosted read and to-read book tracker.

The author's stated purpose:

This app main purpose is to track what you have read, what you are reading and what you want to read.
It acts as a self hosted "personal Goodreads" because I became tired of switching providers every time an online service was shut.
I also became tired of having to export and reimport my data each time with data loss in the process.
You have control on your data since Jelu offers an API you can script or integrate with any third party tool or service (which you cannot do with the vast majority of other online services).
All your data is now located into a single-file database which can be saved anywhere.

If you visit the site you can see a lengthy list of features that include: tracking read books with history and manage to-read list. Many more.

The site describes how to install and get started using it.

I assume you will need to install the app on all of your devices that will need to access the information, and keep the database in an area that can be accessed by your devices.