My librarything lists about 1200 books, and I’m fairly up to date with that. I probably have another 300 or so in storage.
I get rid of a lot, so these are indeed 1200 books that I consciously want to own.
Years ago, my father built me a set of simple bookcases that are taller than usual, which is a life-saver. I remember once looking at a great apartment, and then realizing that we couldn’t live there because the ceilings weren’t high enough.
I checked the 1000 box but I haven’t counted for awhile, so it might be less. There are eight bookcases in the house, and no room for more. At the last city council meeting I asked for shelves at city hall, and we’re starting a library. The mayor is a carpenter and he’s building them. That’s where my overflow is going. I’m more tickled to be rid of them than to acquire them. What are my kids gonna do with them when I’m gone? I only birthed one reader, dammit.
After a rough estimate, I voted for 2000 - 3999. My walls have shelves of books all over. Some people like having posters or paintings on their walls, or cabinets of knickknacks; I like books. It doesn’t feel like home without shelves of books.
No, I collect Gnome Press, a different early sf publisher. It’s small enough to be completist about, so it’s fun to get everything. Arkham lost its appeal for me when I visited a friend of mine who is a high end dealer. He had a pile of half a dozen copies of Lovecraft’s The Outsider and Others. This was pre-Internet when most people had never seen a copy. Takes the fun out of collecting.
Mostly I amass. I read obsessively about everything. I’m also in the 10,000+ category. My library has aisles. 
The last time I attempted a good count, I had over 12,000. But that was about ten years ago so it’s probably up around 20,000 by now.
Over the years, we’ve parred it down to a comfy 200 or so. It seems maybe 90% of them are reference books of one nature or another. We have a zillion interests and hobbies, and so have a lot of reference books.
It’s what we used to look at for information before there was an internet. Not really all that long ago.
Bah! Foiled by strict observation of grammatical rules!
I probably have between 1000 and 2000, though I really don’t want to start counting. I inherited this house from my parents, so I have all of their stuff in addition to my own. My books are probably 75% of the total . . . even though I got rid of some several times over the years.
And don’t ask how much art work I have . . . I could use a few dozen more walls.
I rarely have more than 50 books or so at a time around. I don’t have any room <they’re in big plastic tubs, for the most part> and I either move and leave them behind, or give them to people to read, most of the time.
If I had my own house, it would basically be a library, and I’d never throw any of them away, ever. And I’d probably have multiple copies of my favorites, so I could give those away anyway 
Edit…I have recently come into one book I will never part with, as my dad gave it to me; it was his favorite as a young man, and it really touched him. He recently found it again, and gives it to people he wants to understand him, I think; he’s smooth and charming when he wants to be, but it’s hard for him to put into words what he’s REALLY feeling. This might be the closest he’s come to opening himself up. AND I really like the book, too. Hard to imagine a book about rural life appealing so strongly to a man born and raised in southside Chicago, but…I can see it. He’s always been trying to get back to the land, and it makes our move out West much more understandable.
Also found on Ebay a few stories I grew up with, and I will be taking them with me wherever I go, as well.
Most others are replaceable, and I do not at all mind buying favorite works over and over and over again. I don’t have much spending money, but I’m happy to spend it on books.
2000 +. But I really need to de-bookify.
I counted a couple years ago and had about 3600 so am guessing I’m in the 4000+ range now…I do cull every now and then but it always builds back up.
I sent 8 boxes to Goodwill the other day but am headed to Portland (Powell’s!!!) on Tuesday.
Thousands, most of which are still packed until I can get some more bookshelves for the new place which is why I can’t be more accurate. I have a walk-in closet packed head-high with boxes of books and magazines, for example. The shelves in my bedroom are currently filled with over 500 books waiting to be read.
I’m still trying to decide if I want to have floor-to-ceiling bookcases installed in my office, or just buy four or five 7-foot bookcases.
Wow - have you actually read them all? (Obviously apart from reference books.)
I’ve got three three-shelf bookcases that I bought from Pier One.
Not yet.
/envious!!
I lived in NW Portland, (22nd and Johnson, that lovely Belle-something apartment building) in 87 and OMG, I LIVED at Powell’s! I walked down there at least 4 times a week and just…loved it. Didn’t have the money to BUY anything, often, but they just let me browse all day.
When I order books online, I do it from there, if I can. They will have my business and admiration and gratefulness until I die or someone misses blowing up the Burnside bridge and hits them instead. 
I don’t collect books; I read them. When I’m done I share them with others for the most part. I keep a few I know I’ll go back to for referencing but I live in a small space so I can’t keep many.
I’m sure I have well over 1,000. My problem now is that most available walls in my apartment are lined with bookshelves, and I don’t have very much more room to expand.
Well over 1000 here.
It’s really hard to say. Since I own a bookstore that sells both new and used books, the line has blurred a bit. I’ll frequently take boxes of books from home down to the bookstore, and there’s a constant flow going the other way. If I just count the stuff that I have in the house and my office at the bookstore, it’s probably in the 1,000-1,999 range somewhere.