'IT' was an evil identity with no real shape or form in this world. It expressed itself mostly by messing with children’s minds and altering their perception, giving only those it wants horrible visions or making them do horrible things.
It was also able to take on a 'solid' form when it wished to harm it's victims physically.
And as IT had a taste for children, it used the appearance of Pennywise the clown to lure them and eat their souls. In this state it could also be harmed itself, as was done with the silver earrings and asthma-spray.
Still that was only possible because of the combined faith the kids had in these weapons, not the items themselves (the reason why each of them had to vow that they would stick together no matter what and keep faith in their power as a team).
As for the spider, that was supposed to be a physical form that reflected IT's true evilness. In the book the description of this shape was kept a bit vague, they had to think up something for the movie, so voila big spider.
As the gang eventually destroyed this touchable form (or spider) they did not kill IT but only destroyed IT's capability to enter this world in any form again. ( )

Stephen King does what few others manage to do; he gives you a large number of main characters who are full, rounded characters, characters that you can actually see and care about. It may take him over 1000 pages to do it, but It, as with The Stand, is totally worth it. I remember seeing the movie when I was younger and being scared senseless, and the book was so much better. ( )

'IT' is a mind blowing horror book that has been turned into a movie. Twisted story with interesting theme, from front to back.

Wow, what a book! There's a lot to condense down into a brief review, but more than anything else, the characters made this book. The story was an interesting one, but the characters are what brought it to life. The book was not at all what I expected it to be: a book about an evil clown that goes around killing people. I was surprised by it at every turn, and the fact that it took me a month to read is a testament to how much I enjoyed it. I was so busy with other stuff that I would have ordinarily given up on it, but I stuck with it to the end and it was well worth the trip. ( )

Next to The Stand, this is my favorite Stephen King book. I have reread it several times and could read it many more without growing tired of it. It has a lot to say about childhood, growing up, what we're afraid of and how we overcome that fear. The bittersweet ending always makes me cry. ( )