THIS PAGE CONTAINS SPOILERS RELATED TO HARRY POTTER AND THE HALF-BLOOD PRINCE.
Also, I've had a surprising number of people ask when I'll be starting a sequel to HPDK, LOL. I didn't think I'd dive into writing fan fiction again, but I'm already thinking of something new to write. ;-) I don't know if I'm going to do a sequel to HPDK, per se, but I may write something that directly follows HBP (I will be sad to let Tabitha go - I really enjoyed my character, even if her existence is impossible; when I started writing HPDK, I'd never read the interview with JKR that said how old James, Sirius, Snape, etc were circa GoF, so I didn't know they were far to young to have children any older than Harry is, really). Anyway, rest assured, those of you who want to read something else by me, I will be writing something new. First, though, I have to finish rereading HBP, then I have to reread all the other books. I want to make "my" seventh book as close as possible to the story we already have.
Things in Harry Potter and the Dragon Keepers that, surprisingly or not, turned up in Harry Potter and the Half-Blood Prince:
1. Snape seems to be on Voldemort's side and responsible for the deaths of people close to Harry.
In DK, Snape is responsible for the deaths of Harry's entire extended family.
In HBP, Snape shares responsibility with Peter Pettigrew for Harry's parents' deaths, plus he kills Dumbledore.
2. Draco Malfoy is a Death Eater.
Malfoy is a Death Eater in both DK & HBP; his status as a DE is also questioned in both by a character skeptical of Voldemort's making a sixteen-year-old a DE.
3. Death Eaters speaking against the Dark Lord for selfish reasons, with negative reaction from fellow DEs.
In DK, Draco makes a comment about "finishing the job Voldemort couldn't" (referring to Harry); the Death Eaters are shocked and demand that Lucius Malfoy kill his son for treason.
In HBP, page 33, Narcissa makes a comment about Voldemort's being unable to kill someone (referring to Dumbledore, though at the time, I thought she meant Harry); Bellatrix acts shocked Narcissa would say something like this against their master.
4. Because of Sirius' death, Buckbeak is back with Hagrid.
5. Dragon's blood is very valuable.
In DK, dragon's blood is very important to the Order and the potions they are brewing to use against Voldemort and the Death Eaters.
In HBP, Slughorn remarks on the high cost of dragon's blood.
6. Voldemort will not seek out a fight against Dumbledore, nor is there a LV appearance.
In DK, Voldemort is afraid Dumbledore is not really dead and therefore does not go to Hogwarts for the fight, sending his Death Eaters to assess the situation instead.
In HBP, the Death Eaters are sent as back-up for Draco in his mission to kill Dumbledore (we can only assume that, here too, Voldemort does not go himself so he doesn't have to face Dumbledore on his own turf.)
7. Fred and George Weasleys' business is flourishing and have thus earned their mother's support.
Seriously, who DIDN'T see that coming?
8. Malfoy makes an effort to hide the Dark Mark on his left forearm. Harry notices.
In DK, it's during the Quidditch brawl, and perhaps even during an earlier incident I can't remember. ;-)
In HBP,he hides it in Madam Malkin's shop.
9. With Umbridge gone, Harry doesn't see the point in continuing the DA, though members of the DA do
play a part in the final battle.
In DK, he continues it, anyway, with Tabitha McNoira's help. The whole of the DA arrives for the fight against the Death Eaters.
In HBP, he does not continue the DA, and only a handful of members help out during the battle.
10. Not that they have much significance, but nogtails are mentioned.
In DK, Snape adds pixie wings to a potion when he's supposed to add crushed nogtail hooves; I chose this creature randomly from Fantastic Beasts.
In HBP, page 144, I believe it is McLaggen who mentions having gone hunting for nogtails with his uncle (or possibly grandfather).
11. Both Firenze and Trelawney continue teaching Divination.
In DK, Firenze teaches Divination solely as an extracurricular activity.
In HBP, each teach actual lessons, which are split between the two.
12. Lily's sacrifice for Harry is contrasted with another character's giving up his/her child.
In DK, Lucius Malfoy is willing to kill Draco to save himself. (Incidentally, the very opposite attitude is exhibited by his wife in HBP.)
In HBP, Merope Gaunt-Riddle virtually uses her son in order to keep his father for herself. She let herself die slowly once Tom Riddle, Sr. left her.
13. Harry nearly makes Dumbledore cry.
In DK, it is because of the gift he presents Dumbledore the night before Dumbledore dies.
In HBP, it is because Dumbledore is proud Harry embraces the title Scrimgeour gives him (something along the lines of "Dumbledore's boy").
14. Harry recognizes the importance of telling Dumbledore everything.
15. Ron's birthday and Apparition are mentioned.
As with the Weasley twins' business, this is a given, as Ron's birthday is a milestone, plus Apparition is now a part of the of-age students' lives.
16. Gloves are given as a gift.
In DK, Ginny gives Harry no-slip grip Seekers' gloves for Christmas.
In HBP, Hermione (or Harry? I have only 'H' marked in my notes, LOL) gives Ron Quidditch gloves for his birthday. … Just an odd coincidence.
17. Plenty of Muggle-style brawling, though more so in DK.
18. The Room of Requirement returns as a means for privacy.
In DK, Harry uses it to find privacy to talk to Prongs and Padfoot.
In HBP, Malfoy uses it as a private place to repair the Vanishing cabinet.
19. An adrenaline rush from Quidditch results in Ginny and Harry's (finally!) getting together.
In DK, it is after Quidditch trials, and is initiated by an impatient Ginny.
In HBP, it is after the final Quidditch match, and is initiated by a momentarily carefree Harry.
20. Death Eaters arrive at Hogwarts with the help of an inside man.
In DK, it is with the help of AJ Moody.
In HBP, it is with the help of Draco Malfoy.
21. There is a fantastic final battle that takes place within the walls of the supposedly secure Hogwarts.
22. Dumbledore dies.
In DK, he dies of natural causes.
In HBP, he is killed by Snape.
23. Much success in the final battle can be attributed to freezing/paralyzing the Death Eaters.
In DK, the Weasley twin's Fantastic Freezing Guns are used to this end.
In HBP, the Body-Bind Curse is used.
24. One of Hagrid's beloved creatures dies.
In DK, his dragon from SS, Norbert, is killed by Death Eaters.
In HBP, Aragog dies, of what we can assume is natural causes.
25. The Weasley family endures tragedy.
In DK, both Charlie and a supposedly apologetic Percy die.
In HBP, Ron is poisoned and Bill is disfigured and possibly cursed by a werewolf attack.
26. Hermione is not involved in the final battle.
In DK, she is keeping watch over the young members of the Defense Association.
In HBP, she is tricked by Snape and ends up in his office during the fight.
27. Tonks and Lupin are a couple.
In DK, it is a relatively low-key relationship that exists through the entire story.
In HBP, the actual relationship does not happen until the end, and even then, it may be shaky under current circumstances.
28. Harry pities Malfoy.
In DK, it is because Malfoy's dad is willing to kill his only son for the Dark Lord.
In HBP, it is because Malfoy has clearly been brainwashed by his family and Lord Voldemort.
29. Fire is involved in a wizarding funeral ceremony.
In DK, the body is cremated with magical flames.
In HBP, the body appears to spontaneously combust and leave behind a tomb.
30. The safety of the students and whether or not Hogwarts will remain open are questioned.
In DK, it is decided that the students are more at risk at Hogwarts than at home, so the castle is closed and becomes the new headquarters for the Order of the Phoenix.
In HBP, several students are pulled from the school at their parents' urging and the status of Hogwarts remains unanswered at the book's conclusion.