Here is a list of book apps and book collections.
Free Android Phone app: https://play.google.com/store/apps/details?id=com.amazon.kindle
Free iPad app: https://itunes.apple.com/us/app/kindle-read-books-magazines/id302584613?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/kindle-read-books-magazines/id302584613?mt=8&uo=4&at=10l6SU
Free Mac program: https://itunes.apple.com/us/app/kindle/id405399194?mt=12&uo=4&at=10l6SU
Free Windows program: http://www.amazon.com/gp/kindle/pc
Free Android Phone app: https://play.google.com/store/apps/details?id=com.overdrive.mobile.android.mediaconsole
Free iPad app: https://itunes.apple.com/us/app/overdrive-media-console-library/id366869252?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/overdrive-media-console-library/id366869252?mt=8&uo=4&at=10l6SU
Free Mac program: http://overdrive.com/software/omc/
Free Windows program: http://overdrive.com/software/omc/
Website: http://books.google.com/
Google Chrome app: https://chrome.google.com/webstore/detail/google-play-books/mmimngoggfoobjdlefbcabngfnmieonb
Website: http://www.goodreads.com/
Free Android Phone app: https://play.google.com/store/apps/details?id=com.goodreads
Free iPad app: http://itunes.apple.com/us/app/ted-books/id511071050?ls=1&mt=8&uo=4&at=10l6SU
Free iPhone app: http://itunes.apple.com/us/app/ted-books/id511071050?ls=1&mt=8&uo=4&at=10l6SU
Free iPad app: https://itunes.apple.com/us/app/ibooks/id364709193?mt=8&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/ibooks/id364709193?mt=8&at=10l6SU
Free Android Phone app: https://play.google.com/store/apps/details?id=com.merriamwebster
Paid Android Phone app: https://play.google.com/store/apps/details?id=com.merriamwebster.premium
Free iPad app: https://itunes.apple.com/us/app/merriam-webster-dictionary/id438477986?mt=8&uo=4&at=10l6SU
Paid iPad app: https://itunes.apple.com/us/app/merriam-webster-dictionary/id478132032?mt=8&uo=4&at=10l6SU
Free iPhone app: https://itunes.apple.com/us/app/merriam-webster-dictionary/id399452287?mt=8&uo=4&at=10l6SU
Paid iPhone app: https://itunes.apple.com/us/app/merriam-webster-dictionary/id478126577?mt=8&uo=4&at=10l6SU
Website: http://www.merriam-webster.com/