20 hours!? So why didn't you charge them? Sounds like they have good reason to ignore the costs if they get free help.
Just like a user won't start backing up files until they feel the pain of file loss...
While freely sharing information about the software/processes may seem like it makes you more vulnerable to losing your job, it pays dividends:
Only four books?
That's a little misleading -- I live close to an awesome book store, so I frequently am selling back my books. Also, I read a *ton* online. Most of my reading is electronic these days.
I could understand it if you have a high grade memory and can recall everything you have read that interests you
Yes, I have an exceptional memory, always have. I hadn't thought about that as a possible cause for my bookless-ness. I can't remember exact dialogue all the time, but I can recall numbers with scary precision and the same for major plot points, ideas, etc. I can see a school acquaintance on the street after not seeing them for 10+ years, and just hear a few seconds of their voice and instantly know who it was, even if I didn't know them well at all. Comes in handy.
And if reading is physically or mentally painful for some reason
Naw, both my mom and dad are *huge* readers, and I inherited that. Hell, I used to have a lot of physical books lying around, I just don't anymore. Like I say, lots of reading off a computer screen.
That said, you might want to add the category of 'biblioholics'
Yeah, I kind of overstated my case for rhetorical reasons. I have no problem with people who have an obsession with collecting books. I heard a "This American Life" story recently about a guy who amassed the largest collection of Lewis and Clark books in America. I have no problem with people who collect books with care. I guess it just bugs me when I'm at someone's house and I see their disheveled collection, and I just know they aren't going to re-read 99% of the books in it. It's like a collection by default -- they were too lazy to sell or donate the books, so they piled up.
I cannot conceive that anybody will require multiplications at the rate of 40,000 or even 4,000 per hour ... -- F. H. Wales (1936)