The advantages of this are:
1) It's really painful to read at a slow pace. You work for an hour or two, and the story hasn't gotten anywhere yet, so it's boring.
2) Especially with idiomatic expressions and words that don't have an exact English equivalent, you'll understand the word better if you glance at it eight or nine times in different contexts than if you see it once and look it up and put it on a flash card.
3) You gain reading speed. Don't underestimate how valuable it is to be able to read hiragana and katakana quickly and fluently!
4) If you're reading something you like, something interesting and not too hard, just simply as 'reading' and not as 'language study,' it's more fun and easier to motivate yourself.
5) Research points to the effectiveness of tadoku. Will post more on this later.
The principles of tadoku are:
1) 辞書は引かない （引かなくてもわかる本を読む）
2) 分からないところは飛ばして前へ進む （わかっているところをつなげて読む）
3) つまらなくなったら止める （１ ２ の原則で楽しく読めない本は読まない）
1) Don't look words up in a dictionary - read a book that you can read without looking words up. This doesn't mean you already know ALL the words, but you know enough that you can guess or skip over the rest.
2) Skip over what you don't know and continue forward. Read by putting together the parts that you DO understand.
3) If you get bored, stop. If you can't enjoy a book and follow principles 1 and 2, just don't read it.