There are a lot, and they can get confusing as you read. However, all is not lost. Download the character map as a pdf. Print it out and post it on your ceiling to consult as you read the book.

The cast list is below, abridged here.

BONE bound for CARRIE (though briefly involved with LIZ); friend of CHRISTER's brother BERNARD; not all that he appears to be; Rob's brother; a dark, magnetic blot
CARRIE HARTFIELD CRISCO's sister; raped and killed; Jesus that was awful and I hate to even bring it up, but it won't stay down
CHRISTER CHRISTER his older brother BERNARD went through the ice on a snowmobile; demolished junked cars with his brother with a hammer; possibly an arsonist; jumps off a cliff into the cold water & the dark below and the snow circling around him and falling on his body; compares himself to JESUS; drives his dad's car without permission; might cease to exist at any moment
CRISCO something's wrong with his ear and sense of balance; a shoplifter like us all; his sister, CARRIE, is killed; this changes something in him, brings out darkness (surprise, surprise)
HARRIET her cousin STEPHEN will be arrested for robbing a bank on a snowmobile; plow-driver, sister to TIMOTHY; good friends and maybe more than that with LIZ who's gone; think spark; think plowblade on concrete
JESSE went to prom with LIZ (just friends); lost his index finger and thumb in a bomb-making accident due to accumulated static; goes through the ice after prom with LIZ; went through his deck up to his groin; overall, a pretty minor character, which is strange; may get more lines in the sequel
LIZ / X dead by way of drowning; love interest / conundrum; went to prom with JESSE (just as friends); a central loss; always to be solved for, known as X for cross for crucifix, as variable in algebra, as always marks the spot
MOTHER gone to Canada or cancer; writes often but unintelligibly; the voice of radio schematic; visitor of many shrines; occupies a massive gap; exerts force even in absentia
TIMOTHY HARRIET's younger brother; weird kid; problems in his family life; shoots a cat, maybe ends the world
YR PROTAGONIST the only sensitive character of the bunch, don't you know, even if he's something of a pyromaniac/vandal/phone phreak and has a lot of problems; still we can trust him, can't we?
  There are so many more good ones, but you can't have all the secrets here.