Since I'm behind, I'm using last week's question, saving this week's for later!
Have your book-tastes changed over the years? More fiction? Less? Books that are darker and more serious? Lighter and more frivolous? Challenging? Easy? How-to books over novels? Mysteries over Romance?
I would say that I go through phases in my book reading. The more stressed I am, the lighter the books need to be. If I'm in the midst of personal darkness, the last thing I need is to read dark. Reality is enough on its own.
I also find that as I grow older, I'm more willing to read simply what I like, and not what I am supposed to read. Hence, my current obsession with Regency romances. I don't care whether I ought to be reading something more "edifying". I'm reading what I enjoy at the moment.
I never want to stop challenging myself with new (to me) writers and works. But I'm more aware that I have limited time to read, and I refuse to turn it into a chore.
I read somewhere that with so many wonderful books out there to read, you should give yourself some guideline about how far into a book you will read before you decide to put it aside. Something like "100 minus your age" pages. If a book hasn't caught you by then, it probably won't. Toss it aside, with no guilt, and go on to something else. There are thousands of good choices, and one can't read them all, anyway.
The only exception I'm making to that rule is books I read for my book group. Those I try to hack through, even if I don't like 'em. Point of honor, or something. I'm having trouble with Love in the Time of Cholera. It may be the first book in 8 years that I don't get through.
This makes me sound like I'm only gonna read "fun" books. That's not the case. But I'll no longer apologise for the fun ones that I do read and enjoy.