私は日本語で「ハリー　ポッター」を読んでいます。日本語を勉強するためにハリー　ポッターは教科書より楽しいですよ。

The Japanese reader is going to miss a lot of the jokes in Harry Potter because most names are written only in katakana. This rendering provides a general pronunciation of the English, but no clue to the meaning of the names. So all the puns and wordplay are lost to the Japanese reader. While this might not make a lot of difference in other books, it's a major component of the humor in the Harry Potter series. Unfortunately, even if you read Harry Potter in English, you might not understand the words because they're invented and not in the dictionary. So I'm going to try to explain some of jokes.

Hogwart's Four Houses

グリフィンドル Gryffindor

A griffin is a mythical beast often used in heraldry (coats of arms). Some people think the "dor" is short for French "d'or", meaning "of gold" 金 [きん]. So Gryffindor might be "the golden griffin". It gives the impression of nobility, like the golden lion on the coat of arms of the British Royal Family, especially King Henry II.

レイブンクロー Ravenclaw

Ravenclaw means the claw 爪 [つめ] of a raven 烏 [からす]. (Actually ravens are a little different than crows.) Ravens are associated with death, and so often looked on as an omen of evil. In fairy tales, ravens guide the hero through the passages of the underworld. Christians probably connected the raven with witches because it is a totemic symbol in Norse paganism. However, witches are good in the Harry Potter books. Oddly, on the Hogwarts coat of arms, the symbol for Ravenclaw is the much more noble eagle.

スリザリン Slytherin

Slytherin is a made-up sound-effects word which sounds like "slithering" 「にょろにょろ」, "to slip or slide like a snake". Ever since the serpent tempted Eve in the Garden of Eden, the snake has been a symbol of evil in Western Literature. Slytherin is a house of snakes "cunning folk (who) use any means to achieve their ends." Most of its members have evil-sounding names.

ハッフルパフル Hufflepuff

Hufflepuff sounds soft and fluffy, the opposite of hard and substantial. This is one of the few names that doesn't lose much in transliteration as it is basically a sound effects word."Huff" means "to emit puffs, as of breath or steam". In the story of the Three Little Pigs, the big bad wolf says, "I'll huff and I'll puff 一吹き [ひとふき] and I'll blow your house down." "Puff" means "a fluffy mass" or "pouf"--like a powder puff パフ. Magicians often disappear in a "puff", a cloud of smoke. Poof! If you are "in a huff", you are swelled up in anger ぷりぷりして. Cartoonists often draw people in this state with puffs of steam coming out of their ears.

The symbol for Hufflepuff is the badger, which is sort of like a tanuki.