I agree with pizzagirl. With all the reading I do, books would quickly overtake the house if it weren’t for the lending library. I’ve saved tons of money also, some of which I’ve donated to the local library. Sure I have to wait before getting the latest must read, but there’s so much to read while I’m waiting.
^ D1 did so much reading that we gave up on book store gift certificates and surprised her one Xmas with an armload of borrowed library books. Kindle saved her.
My books have overtaken the house.
I’ve got around 1000 books in the master bedroom, more in the hall, the laundry room, the attic, the kitchen, the office, the basement and the boy’s room… One year one of my kids was asked to count the books in the house. They came home and burst into tears. Luckily the teacher was fine with an estimate of the number of books in their room which was probably several hundred. I toss books all the time, but obviously there are still an awful lot of them!
I love my books. I bought my house because it had a library. When I saw that I was sold. I love re-reading my favorite books. I donate books I didn’t much like or that I know I won’t read again. Reference and non-fiction books I keep.
We purged our books before moving, but from the stack of still-taped-shut boxes of books here in the office/spare bedroom, you would never know it. I truly believed that I had eliminated enough books to account for the bookcases I didn’t ship. Boy was I wrong.
But, there are no dollar bills in any of them, so when the time comes Happykid can safely drop them all off at the Friends of the Library book sale and not look back.
One of my kids had that book counting assignment in 3rd grade. We had 638 kids’ books. The teacher didn’t believe him and confronted me about it. Just one of many issues with that teacher that year…
Ha ha! Reminds me of a reading questionnaire I had as a kid. Among the Qs: Do your parents encourage you to read? My answer: No, they try to get me to stop. 
Reminds me of a readathon we had at kids’ school–get pledges per page for the # of pages read in a specified hour at school. My kids could only get flat rate pledges (eg $10 or $20 for participating)–no one would pay my kids per page. Each read an entire 200+ page book in the hour.
An idea. One of my very sweet octogenarian neighbors has a book shelf (actually an old library cart) by the sidewalk. “Free to gentle readers”. He only wheels it into the garage during rainy days.
My inlaws have a huge house and my MIL has a habit of squirreling away valuable items in pockets and drawers and books and such. My SIL and I were in the attic and I looked around and lamented about all the work we would have to do when they are gone. My SIL (their daughter) said, “Ninety percent of this stuff is going straight to the Goodwill.” And I said, “Aren’t we going to go through it? What about all the stuff Mom squirrels away?”. SIL says, “Well, if someone at the Goodwill finds a $100 bill in a pocket, it will be their lucky day.”
MIL would have a fit if she knew SIL didn’t plan on carefully going through everything and cataloging it. But MIL will be gone and thankfully none of the siblings need to financially worry about accidentally making a large donation to the Goodwill. And I am relieved that we won’t have to worry about what happens to every little (or big) thing in the house.
The good thing about being a teacher is that you can put the books you have finished reading on the table in the teachers room, and they will be gone by the end of the day. Our staff room actuall had a bookshelf in it for that purpose. I don’t keep books. If I like a book, I want to share it with others. IF I don’t like a book, I can’t wait to get it out of my house.
I have shelves and shelves and shelves of books from the bookstore and stacks of books from the library; I don’t buy from Amazon. My library system has a good selection of ebooks that I take advantage of, but I prefer “real” books.
Some day my children will have to deal with my books. That’s the way it goes.
Some specialty bookstores may be interested in a collection of mysteries or SF. There are also smartphone apps that will help in determining value.
One of my retirement plans is to go through my books. I have accumulated quite a lot over the years with a career in and around publishing. Some of my books are modern first editions and some I know are valuable. What makes them valuable is that they are first editions by authors or illustrators who went on to greater prominence later in their careers. Some are signed although signed books if personalized can bring down the value. However I do have a signed first edition by both Woodward and Bernstein for “All the President’s Men” along with a signed first edition with a banjo illustration sketched by Pete Seeger of his “incompleat Folk Singer”.
Thinking about the news that Harper Lee is to publish an earlier written book while probably everyone here has paperback copies of “To Kill a Mockingbird” somewhere out there is someone with a first edition hard cover of the book. There are probably many people like me that have multiple hardcovers of the Harry Potter books including ones from the U.K but one of mine has a bookplate signed by J.K Rowling.
One of my friends was browsing at the Friends of the LIbrary $1 table a few years ago and was able to purchase a signed copy of Golda Meir’s biography.
In terms of rare books that is something else entirely. My brother was interested in rare books and after he passed away I did inherit a good deal of authors that he had collected including a collection of about 6 or so poetry titles by Sara Teasdale. At the time, younger d was at one time working in a store that had used books/rare books/Americana/ephemera and on consignment the dealer was able to resell this collection resulting in a check for me that if I recall might have been around $2000. It did take a month or so for him to find the right buyer but it was worth it. Of course he probably made a lot more money on the deal than I did but it was a nice check and even better these books are not sitting in a carton in my basement. I recall that at one time he was interested in Henry Clay and donated a collection to something like the Henry Clay Historical Society. No money, but he did get a nice letter and a tax write-off.
Consoloation: My much-despised fourth grade teacher wrote on my report card, “Arabrab has 11 library books in her desk.” And she did not mean it as a compliment. Mom used to push me outside and lock the door so I would go play rather than reading.
Update from OP…my dad’s books are out of the house. Team effort of siblings and a BIL and a grandchild. Older neighbor spent one hour looking through shelves before getting overwhelmed . He took one box of books and went home and never returned. But he kept saying great things about my dad and it became obvious they had shared a good friendship. My dad has been dead for 15 years and this neighbor still cherished their shared love of books. We flipped through some books but not many, and never found any cash.
The MIT Science Fiction Society would probably be happy to have your collection of scifi, http://www.mit.edu/~mitsfs/
My grandfather had tons of books! And a house with tons of bookshelves (everything was neat and orderly). I loved visiting my grandparents because it was like a candy store of books. My mom always said he lent his books out freely (he expected to get them back but often didn’t) and through the years his book donations were actually the basis of the local library.
When he died, my parents sold them en mass to a book dealer and as in post 15 I’ve wondered what was between all those pages. (In consideration of my parents they were too worn out at the time to think straight.)
Well, H and I loaded up our collection of old books (many older than 100 years, all in decent condition) and took them in to be appraised at a well-respected dealer of old and rare books. Unfortunately, ours were old but not rare - but at least I got rid of them.
We sold them for about $1-$3 a book, and the dealer said that most will be purchased by designers or others who just want to fill a bookcase with nicely-bound books. I guess there’s not much of a market for Dorothy Vernon of Haddon Hall.