WARNING: Don’t read this post if you are reading the book or planning to read the book in the future.
I have finished reading the book. It is quite hefty, just as the previous one (book #5) and not as exciting as book #1, 2, and 3. The story line feels dragged and does not flow very well. Real excitement happened only in the last chapters, in which Dumbledore died because Snape cursed him with “Avra Kedavra” and got buried (shame..). So I am pretty sure that he is dead 100% this time and can’t be saved by his crying Phoenix or other means. Although, I might be completely wrong here.
When I finished 50 % of the book, I had a strong feeling that the Half-blood Prince was Voldermort. That was proven to be really wrong. It was Snape after all. At the end I am just as confused as Harry, Hermione, Ron, Prof. McDonagall, etc about Severus Snape. Is he or is he not one of the good guy?. Well, I guess I have to wait another 2 years or so for the answer.
The rest of the book is mainly about how the friendship between the characters is starting to change into a relationship and the dilemma that they face. Harry and friends are growing up.