Unless your grown kids are professors, they generally don’t want your books. Books have been replaced by Netflix, lap top computers, Kindles and the Internet. Books are heavy, hard to lift and take up valuable space in our ever decreasingly sized homes.
Just because you have a set of books, they are rarely rare and rarely worth anything.
If you think the book is relatively common, plug the title, author, year of publication, and publisher into a search engine such as Biblio.com. Once you have background information, call a book antiquarian.
Photos and other paper ephemera
Although a valuable link to the past and have great sentimental value, old photos are not worth much unless the sitter is a celebrity, is linked with an important historical event or the subject is extremely macabre, like a death memorial image.
Family photos can be useful but not mountains and mountains of them. An option is to take digital photos of your photos and email to your family.
Old greeting cards are not valuable unless handmade by a famous artist.
Postcards are valued mainly for the stamps.