Readers - do you keep a note of every book you read?

Yes! I keep a book journal, and I also post them on goodreads. I write down the name, author, when I read it, and rate them 1-10 and a brief comment. Have never re-read a book, only to discover I've read it before.

No I don't make a note, I generally know whether I've read a book or not. I have a bunch of authors and I read their books as they are released.

The only exception to this is if I "discover" a new author after they have already written multiple books. for example, last year my FIL got me onto Ian Rankin so there is a huge back catalogue for me to read. The first thing I did was google his Rebus books so I knew what order they were written. I made a note on my phone of the books in order, then as I read them I mark them off. I also put them in order on my Kindle so whenever I want to read one I know that it is the next one on the Kindle.

I don't bother with listing books I've read, it takes away from reading time.

I've been using Goodreads for a few years now and I really like it. I don't post long reviews, but I do rate the books I finish. My husband has an elaborate Excel spreadsheet separated by genre, date, rating system.

Yes, I keep both a paper list and my Goodreads updated

I don't. When I used to buy physical books nothing pissed me off more than to buy a book and after a chapter or two realize I'd already read it. I solved that by looking at the publishing date and just didn't buy older books. Since I've had a Kindle starting way back with the Kindle 2 I buy all the books I read through Amazon. The cool thing is that if I try to buy a book I've already bought it tells me before I buy it again

I read too much...too much time keeping track

I just signed up for Goodreads... When I was a child/teenager I'd keep a list - it was books I wanted to read and I'd just cross them off as I read them... Now I've gotten into the habit of buying books that I want to read... Slightly more expensive option that a list and a library card...lol

I use Goodreads. I've never gone back and updated it with all the things I've read in the past but when I see a book that I've read on one of the lists, I'll just take a second to mark it as read then. I'm not really worried about rereading books as I tend to remember what I've read.

The main reason I like to use Goodreads is to keep track of books I want to read. My public library has this feature but it's annoying when a book is not part of the library's holdings.

I keep a list on Goodreads. I love to go back and look at what I read. Especially when people ask me for recommendations. I have a favorites shelf just for that.

That's the same for me too.

I've been reading one or more books per week since I was about 15, I've never forgotten what I've read and started to read it over. It's probably because of that that I have never felt the need to write down what I've read or keep track in any fashion. I have started a Good Reads account but I never remember to log in. I mostly wanted it to keep track of books I want to read or books that are in a series that haven't been released yet.

I've created a wish list on Amazon.com where I've listed all the books that I've read this year.  I also have a separate wish list for the books that I've read last year.  

This way if I try to add a book to my wish list that I've already read Amazon will tell me.  

Another fan of Goodreads. I rate each book I read and organize the books on shelves there. I'm nerdy enough that I like going back and looking at shelves from previous years.
Before Goodreads, I kept a paper/pen reading journal.