In my experience, I find I miss too much detail from the books I'm reading if I read a book a week. I find reading 1 book every 2 weeks allows me to mow through a decent number of books while still allowing me to take some time out to really think about the concepts and ideas and experiment with them in my life as I’m reading. I'm also fairly selective of what I read. If a book is not terribly profound I tend to lack the motivation to continue reading, so I try to make good choices rather then just read a book because it "may" be good or "looks" interesting.
There are times when I take notes when reading, but I find it really interrupts the flow. I may gain more notes, but I get less out of reading. I find if I want to take notes it’s best to read the book a second time, or at the very least, take very brief notes (ie. a few words, a page, and a paragraph number relative to the page) so that you can go through the book later and more fully flesh out your notes if you need/want to.
When I take notes in that manner I write down the page number, the number of the paragraph(s) that had whatever I found interesting, and a few brief words (brief enough to not take too much time to jot down, but detailed enough to jog my memory later when I go through the notes). An example of a note may look like this:
p59, par 3, I like how this idea relates to productivity.
Often my notes consist of how one concept relates to another, so I find it important to jot down a few words with your notes, otherwise I forget what I wanted to note down when I go through my notes once I'm finished the book.
As for implementing ideas from books, I’m still working on this one. What learnt recently is that while I can get many great ideas from what I read and have loads of notes, the large majority of ideas aren’t really what I need to be focusing on at the moment (ie. they just aren't high enough leverage or aren't important enough to warrent my attention).
Often I can tell whether or not I should be focusing on something else by my thoughts. If I'm trying to implement an idea and I keep thinking of another idea, it's usually a subconscious message saying "this path is no good, try another one". Usually this happens when I've lost my awareness of the present moment and I'm trying to race off into the illusionary future to "find myself" in some form by gaining new information. New information is good, but without proper grounding, it can become an endless quest in denial of the present moment and the
real work you should be doing.
But that’s one of the reasons I like to buy books instead of loaning them from a library. If I read a book I don't find immediately useful but then later think of an idea from it that could be useful, I can re-read it very easily since I still have the book available. An expensive practice to be sure, but it's not too bad if you focus on buying quality books that you'll be able to gain new insights from, regardless of the amount of times you've read them.
I'm sure some may disagree with me there, but I liken reading with the exploration of a piece of land -- a search space. Much like a forest can never be fully explored in your first pass through, a book often requires you to “trek through it” multiple times before it exposes its most interesting secrets.