I confess to not (yet) having read the first "Harry Potter" book, Harry Potter and the Sorceror's Stone, and so I can say with certainty that it is not necessary to read that book in order to fully enjoy the second one. This book has sturdy enough legs to more than ably stand on its own. It is a book filled with the writer's imagination, so much so that it cannot help but in turn spur the imagination of the young who read it. I enjoyed it as an adult but found myself wondering how much more I would enjoy it if I was as old as its "target" audience.
Perhaps much more. I recall reading (and being enraptured by) the old "Wizard of Oz" books by L. Frank Baum (there are many, not just one), feeling that I was right there in Oz beside all the wonderful characters, sharing fully in their adventures. There's no doubt that the youngsters reading of Harry Potter feel that they, too, are walking the halls of Hogwarts (Harry's school) beside him. I'm a bit jealous of that power of young imagination, much of which we shed as we get older.
Harry Potter and the Chamber of Secrets opens with Harry pining for the end of summer recess so that he can return to Hogwarts. It is there where his friends are, and it is there that he is happy. There is no happiness in the home in which he lives with his uncle and aunt, the Dursleys, where he is in general looked down upon and mistreated. Harry's own parents are deceased and he has been taken in by his uncle and aunt, who treat him as a second-rate citizen. Shades of Cinderella. They might even treat him worse than they do except that they fear his powers of magic.
There is as much humor in Chamber of Secrets as there is imagination. Harry is told by his uncle (on Harry's birthday no less) to go to his room and there remain perfectly quiet while the Dursleys entertain some guests. While in his room, Harry is visited by Dobby, an elf-like creature who warns Harry not to return to Hogwarts as danger awaits everyone there. Dobby, not the quiet type, begins to make a racket, much to Harry's profound dismay. Harry attempts (and fails) to keep him quiet. Needless to say, the Dursleys are ultimately not happy with Harry as much (humorous) destruction occurs.
With Dobby’s warning to Harry that danger awaits him in Hogwarts, the book becomes as much a mystery as a fantasy. Once in school again, there are signs (literally scrawled messages on the wall) that the Chamber of Secrets will again be opened and the evil contained therein again set loose. Children are later frozen (shades of Medusa) and very nearly killed by something unseen crawling the halls of the school. It is up to Harry and his friends, Ron and Hermione, to discover what it is and to stop it.
As with most good mysteries, the culprit is a surprise. The battle that occurs in the hidden Chamber of Secrets at the end is quite intense and might be extremely frightening to sensitive (and younger) children. It feels almost as though Stephen King donated a few lethal paragraphs to the book's ending. Still, the "classic" fairy-tales have children almost eaten by wolves or thrown into ovens to be cooked and so it could be said that J.K. Rowling is merely returning to the classic form of children's storytelling. But for those parents who might not want their children to read such intense scenes, be forewarned.
Along the way, there are enough surprises and imaginative details thrown in as would normally fill five lesser books. There is the magic way Harry is supposed to travel to school (on the subway platform) and then, when he fails to make his train, the adventure with the flying car, culminating with the Whomping Willow's distress. The subjects of portraits on the walls in Hogwarts now and then disappear to have their hair done or spruce themselves up in some other way. One ghost haunts nothing else but a girl's bathroom in the school, and a wonderful diary that can write back to you as you make entries -- like having a friend in your pocket, as one character says. A broken wand creates (inadvertently) many incorrect (and funny) circumstances as magic spells backfire, and one egotistical teacher's lack of talent quite often does the same. There is the magic of "Floo powder," by which a wizard can travel anywhere through the fireplaces of buildings as long as one states the destination clearly (if not, who knows where you’ll end up, what hearth you’ll tumble out of?) and clocks that have no numbers but rather say things like: "time to make tea" or simply "you're late". It is all of the details (those mentioned here and many more) that truly make Harry Potter and the Chamber of Secrets a wonderful book, a book that is a pleasure for adults to read but which will for a child prove to be a true and memorable joy.