Harry and Ron are in deep trouble. After using Ron's father's flying car to fly to school, both get detention, and Ron gets a screaming letter from his mother. Harry's detention is to help Gilderoy Lockhart answer his fan mail.
Lockhart is an annoyingly self-obsessed professor, who has captured the hearts of a very large segment of the magic population. He is the author of many popular magic books and receives a lot of press. His intense superficial charm is balanced by his arrogance towards the people with whom he interacts directly. His professorship replaces that of Quirinus Quirrell, last seen in the previous book. Quirrel was possesed by Voldemort, and was thus the antagonist. Harry defeats Voldemort (sort of, read the first book to find out how), which causes Quirrel to die.
Later, Harry, Ron, and their overachieving friend Hermione go to the party of a dead person. Apparently, even the dead have parties, social cliques, popularity contests, and other tiresome attributes of life. The party turns out to be a bust, when crashed by a hunting party, who rubbed in their rejection of the host as being worthy of joining their party.
So it goes. The important theme by now is that Harry hears disturbing whispers that eventually lead him and his friends to the scene of one of the faculty's murdered cat. At the same time, they see words on the wall that warn the "enemies of the heir" [because] "The Chamber of Secrets has been opened" (pg 138). I am about half-way through the book, and aside from the bedroom elf scene, nothing in the story arc has gone beyond the minor scrapes that Harry and company get into. I'm expecting an acceleration in the timeline, since I'm half-way through, and the book says that is around Halloween, with November through May to still get through.
Thankfully, the book is a fast read, having spent maybe two hours to get this far into it.