I've been buying books since I was a teenager, and when I was working for Lauriat's and then Border's Books my collection grew. But as I've grown older I've downsized a bit, trying to make things a little easier for my relatives when I'm no longer here.
I still buy books though, although now they are ebooks on my Kindle Fire Tablet. Lately I decided I wanted an inventory of those ebooks, so I started using the Google Spreadsheet app to do it. I must admit I am a bit rusty since it was about a decade from the last time I used Excel but I seem to have recovered what skill I once had and I've become more confident as I go along.
I've divided my ebook "library" into three separate spreadsheets. The first is Nonfiction Ebooks which includes History, Biography, Mythology, Religion and Philosophy. That comes to 222 books so far listed alphabetically by author.
The second category is Mysteries which I'm still working on. It's also alphabetical b y author and is over 194 books even though there are only 5 authors on it. (They all are quite prolific.)
The third spreadsheet will be Science Fiction and Fantasy, and that should be the largest list.
Of course, I'll need to add newly purchased books.