As as of season 5 with Game of Bones house Frenchie shit just got real Game of Thrones shirt, TV series have extensively deviated from the original storylines of the books. In many cases Series have actually moved beyond the books. So, it means you would be able to enjoy two different endings, if you do both the things. If you want to go for this last option, I would suggest you to read the 5 books, prior to watching the series. the other way round, i believe can be confusing and boring !!