I watched all series in the time since Series 5 started.
Series 1-4 were much, much better than series 5 IMO.
Yeh this is definitely the weakest season, though the last three episodes were probably up their with the shows most 'heart-stopping'. I haven't read the books, and won't do until the series is finished - it's hard enough following one confusing storyline never mind two!
But from what I've heard, this season was the first to drift away from the books more frequently - with some things that happened in this season not happening in the books at all? A bit disappointed their was so much time spent in the East with Danerys (sp?) - where nothing actually happened until episode 4 or 5, as I'd have thought Brann's story north of the wall would have been picked up again.
I kind of hope the books/series keep Jon dead, though I can see him coming back.