I'm going to echo what Misty just said. To kill your main protagonist off midway through the book is a bold move, but not just because of the shock factor. I'd personally be concerned that my reader may not have developed the attachment to the character necessary to effectively pull off such a move. Sure, you've been with the character for what seems like forever, but have you truly given the reader all that he/she needs to care about this character dying? Most main characters who die in television shows do not do so midway through the first season, possibly for this reason. I also have to wonder, if he dies after the first half of the first book in the series, is he truly your main protagonist in the first place? I fear that readers may not see it that way, as they don't know (hopefully) that he'll be back. Surely someone will step up to fill the gap? Last comment/suggestion: when the character(s) come back, please let there be consequences, as others here are mentioning. An underexplained or deus ex machina-like return from the dead feels cheap and easy. Over the course of my planned series, a lot of characters die, but only one comes back. When he does, he's got a limited time, since his body continues to decompose (gross, but what're ya gonna do?). Make death matter; make resurrection messy.
