I read books for leisure without thinking, just for the pleasure of it, but if I'm reading books to edify then I'd better try to get the most out of it that I can. If I read a fantastic book, then I should re-read that book within 10 years and I find I get some multiple of its original benefit.
I've always felt distubred that books I read years ago (or even earlier this year) are essentially lost to me; I forget, I fail to apply, I cannot find that half-remembered reference. For making notes on books, recoding impressions and quotes, I've started using
Zotero, a firefox addon which seems comprehensive and exports an xml file so (with data migration every decade or two) the information can be retained for the rest of my life no matter changes to IT infrastructure. There are other such software out there if you don't use software. See here for a
.
In my library I only keep books that I know I will want to read again or I want my children to one day read; otherwise I either give it away or throw it away depending on its quality.
One last thought: I find that I can read an edifying book "in the Spirit" or just in my own strength. If I'm reading it right, which means slowly enough and prayerfully enough, then I have a discernable sense of great benefit. If I don't get that sense, then maybe I'm reading the wrong book. Through my Christian life I have found that God has led me to exactly the right books much more often than not.