Back in college (due to years of working libraries and having access to Friend of… discards) I had about 10,000 books.
I thought of myself as a collector. I loved books. Each was a precious object and to discard it would be to leave a hole in my collection. Then I took a class offer by a local antiquarian bookseller.
He started the first session by saying “Most of you here are not book collectors, you are book accumulators.” Something about that stuck with me and ever since I’ve never had any trouble at all getting rid of books (and then my library science degree did much to convey that few books are artifactually interesting and only have value so far as they are filling a need).
I suggest you pick ten crappy paperbacks that you must admit you’ll never read again and go throw them in a dumpster. Don’t donate them. Don’t try to convince a friend that they want it. Just in the trash, eventually to be shredded and pulped and turned into toilet paper. Wait a week to be sure the world doesn’t end.
Then go through the collection and box up anything you admit you’ll probably never open again and can’t create an artifactual reason (actual market value or personal emotional value) and get those sold or donated.
For those on the border where you think you might actually have some use for them, but probably not, put them in a box, close the box and write a date 2 years in the future on the box. When that date arrives, donate or sell any books still in the box (it’ll be all of them).
The end result will be a library that is actually useful to you. You’ll know what’s in it and what’s in it will be valuable or useful to you.
But if you have to have them all, then many of the indexing tools listed above are good. Just make sure it is something you can access remotely because it won’t do you any good to have a nice database at home if you are standing in Barnes & Noble.