I got rid of my Google account last year, and I generally avoid Google products. I use Maps sometimes when I'm not using ArcGIS, and that's about it. So this is probably going to be pretty biased since I'm not a Google fan.
I think I read a newspaper clipping once from Google Books, and that's about it. I'm satisfied with my library and Amazon/Kindle for reading e-books, and Goodreads for organization, shelves, reviews, and finding new titles. My library lends the classics with no waiting list, and Amazon has them for free too. I've also used openlibrary.org, and found them to be great for scanned classics and sometimes I get lucky and can checkout a book that isn't in the public domain. As for the books I'd rather have in print, well I can usually buy them for cheap from Amazon as well (I don't mind used books)...I recently bought a history textbook I used in college (I really wanted to read it again) for $0.49. Not to mention I usually get Amazon gift cards for my birthday or Christmas, so it's easier to just stick with them. I also like my local used bookstore for the thrill of the hunt

.
I took a look at Google Books just now, and the interface is not intuitive to me. The free sample is clunky and frustrating -- I like Amazon's "Look Inside" much better, and I like that the reviews are on the same page. I like their website in general better as well, because it's easier and more intuitive to navigate, but maybe that's because I've been using it for years.
I much prefer the feel of these:
Amazon
Goodreads
Open Library
to these:
Google Books
Google Play
I don't read many magazines beyond my subscription to Nat Geo, but when I do, I use Zinio for reading magazines online (free, courtesy of my library). Google's
magazine section is pretty cool, I'll give them that. I see some things that I can't get on my library's Zinio account that I'd like to browse. I still don't like the reading pane, though -- no true full screen with my web browser.
I do believe in open access of information, so I can't bash them too much. I appreciate what they're doing with their book scanning project and how some books are searchable. I just personally prefer other things that work better for me (like Open Library if I want a scanned copy)....that and I just don't like Google very much. To each their own though -- what's important is that people are reading.