Dad had A LOT of books. A total of 26 book boxes to be exact, and I only finished packing them today. Half of them have already been transported home, and the other half are going home this weekend. I didn't have the time or energy to go through each book individually to see if I should keep each one, so much to my husband's chagrin I erred on the side of packing them.
But even I had to admit that a few of them would just never find a reader. Some were outdated factual tomes, for example, on buying houses or building environmentally conscious buildings. There were also ones that were so above my head that I had to be honest about and throw out. These included all of the computer engineering books (most likely outdated as well) and books on topics such mathematics for physics or advanced chemistry. All of these books were recycled.
I still feel really overwhelmed by how many I kept and the impossibility of reading some of them and sorting all of them in a sensible amount of time-- say before our next move.