I read the first novel in the Harry Potter series, ''Harry Potter and the Sorcerer's Stone,'' in April 1999 and was only moderately impressed. But in April 1999 I was pretty much all right. Two months later I was involved in a serious road accident that necessitated a long and painful period of recuperation. During the early part of this period I read Potters 2 and 3 (''Chamber of Secrets,'' ''Prisoner of Azkaban'') and found myself a lot more than moderately wowed. In the miserably hot summer of '99, the Harry Potters (and the superb detective novels of Dennis Lehane) became a kind of lifeline for me. During July and August I found myself getting through my unpleasant days by aiming my expectations at evening, when I would drag my hardware-encumbered leg into the kitchen, eat fresh fruit and ice cream and read about Harry Potter's adventures at Hogwarts, a school for young wizards (motto: ''Never tickle a sleeping dragon'').

For that reason, I awaited this summer's installment in J. K. Rowling's magical saga with almost as much interest as any Potter-besotted kid. I had enjoyed the first three, but had read the latter two while taking enough painkillers to levitate a horse. This summer, that's not the case.

I'm relieved to report that Potter 4 -- ''Harry Potter and the Goblet of Fire'' -- is every bit as good as Potters 1 through 3. It's longer, though. ''Goblet'' is as long as ''Chamber'' and ''Prisoner'' combined. Is it more textured than the first three? More thought-provoking? Sorry, no. Are such things necessary in a fantasy-adventure aimed primarily at children and published in the lush green heart of summer vacation? Of course not. What kids on summer vacation want -- and probably deserve -- is simple, uncomplicated fun. ''Harry Potter and the Goblet of Fire'' brings the fun, and not just in stingy little buckets. At 734 pages, ''Goblet'' brings it by the lorry load.

The most remarkable thing about this book is that Rowling's punning, one-eyebrow-cocked sense of humor goes the distance. At 700-plus pages, one should eventually tire of Blast-Ended Skrewts, Swedish Short-Snout dragons and devices like the Quick-Quotes Quill (a kind of magical tape recorder employed by the satisfyingly repugnant Daily Prophet reporter Rita Skeeter), but one never does. At the least this reader did not. Perhaps that's because Rowling doesn't dwell for long on such amusing inventions as the Quill, which floats in midair and bursts out with florid bits of tabloid prose at odd moments. She gives the reader a quick wink and a giggle before hustling him or her along again, all the while telling her tale at top speed. We go with this willingly enough, smiling bemusedly and waiting for the next nudge, wink and raised eyebrow.

Puns and giggles aside, the story happens to be a good one. We may be a little tired of discovering Harry at home with his horrible aunt and uncle (plus his even more horrible cousin, Dudley, whose favorite PlayStation game is Mega-Mutilation Part 3), but once Harry has attended the obligatory Quidditch match and returned to Hogwarts, the tale picks up speed.

In a Newsweek interview with Malcolm Jones, Rowling admitted to reading Tolkien rather late in the game, but it's hard to believe she hasn't read her Agatha Christie and Dorothy L. Sayers. Although they bear the trappings of fantasy, and the mingling of the real world and the world of wizards and flying broomsticks is delightful, the Harry Potter books are, at heart, satisfyingly shrewd mystery tales. Potter 3 (''Azkaban'') dealt with Harry's parents (like all good boy heroes, Harry's an orphan) and cleared up the multiple mysteries of their deaths in a way that would likely have pleased Ross Macdonald, that longtime creator of hidden pasts and convoluted family trees.

Now, returning to Hogwarts after attending the Quidditch World Cup, Harry and his friends are excited to learn that the Triwizard Tournament is to be reintroduced after a hiatus of 100 years or so (too many of the young contestants wound up dead, it seems). Aspiring wizards from two other schools (Beauxbatons and the amusingly fascistic Durmstrang Academy, location unknown) have been invited to spend the year at Hogwarts and compete in the contest, which is composed of three beautifully imagined tasks. These can only be performed well by contestants who can solve the riddles that bear on them; both children and students of Greek mythology will enjoy this aspect of Rowling's tale.

Like the Sorting Hat, one of Rowling's early ingenious bits of invention, the Goblet of Fire is essentially a choosing device. It's supposed to spit out three flaming bits of parchment bearing the names of the three contestants in the tournament, one entrant from each school. In a vivid and marvelously tense scene, the Goblet of Fire spits out four parchment fragments instead of three. The fourth, of course, bears the name of Our Hero. Although Harry is supposedly too young to compete in such a dangerous series of tilts, the Goblet has spoken, and of course Harry must step into the arena. If you think young readers won't lap this up, you never had one in your house (or were one yourself). Adults are apt to be more interested in just how Harry's name got into the Goblet in the first place. This is a mystery Rowling works out with snap and verve. And, unlike the denouements I remember from the Nancy Drew and Hardy Boys mysteries of my youth, where the culprit usually turned out to be some vile tramp of the lower classes, the solution to the Goblet mystery, like the answers to the Triwizard riddles, struck me as fair enough.