And I have to say I've tried it. When I was 13 I wrote a multi-MC book. It didn't really work out for plenty of reasons -- lack of character development, total angst-fests on every other page, plain old bad writing, and, I think, the whole multi-character thing, to name a few.
I had five "main characters" to begin with, but a few chapters in it became clear that I was developing a favourite, and this favourite was dominating the page-space. Eventually one character disappeared almost completely when his plot sputtered out and I got bored.
Obviously, the author of the book I'm reading now is not thirteen, and as such did a much better job of planning out the plot distribution. But the problem of favouritism remains, not from the author, but from the reader. I've started to like some characters better than others. I can relate to Character A better than Character B and Character L's problems are way more interesting than Character M's. As such, I want to read about Character A and L. When Character B and M show up for their respective scenes, I find myself skimming, waiting for the story to get back to something I care about, which isn't all that great.
This brings me to another problem. With so many characters to cover, there's not a whole lot of time for character development. There's a lot of telling rather than showing, and I'm not interested in Characters B and M because the author doesn't have time to make me interested. If Character A didn't happen to be in a situation I can relate to, I probably wouldn't care much about her either. If I hadn't been told that Character B had political views that were the complete opposite of mine (or if there had been time for him to show me he had some redeeming qualities), I might actually be sad when his brain got eaten. In other words, the reader suffers a certain lack of emotional investment in the characters and their lives.
These are all bad things. It makes it too easy for me to put the book down. In fact, at times, when I look at the number of pages there are left, I think I might not even want to finish it. Anf of course, the absolute lastlastLAST thing an author wants a reader to do is put the book down and never pick it up again.
So to sum this all up, the trouble I run into with multi-MC books is as follows:
1) Readers (and sometimes authors) develop favourites.
2) Readers (and sometimes authors) have some characters that are definitely less than favourites, and must suffer through scenes that involve those characters and no others.
3) Chronic amounts of telling are often present in an attempt to quickly develop characters and relationships in the limited amount of page-space.
4) Readers have a lack of emotional investment. In other words, they don't really care what happens to any of the characters - even their favourites - because they never had time to really get to know any of them.
5) Zombies jumping out of shadows, chasing after the protags, and eating their friends' brains gets old quick, and never comes across in a book as well as it would in a movie. (Because movies have soundtracks and can have various stringed instruments screech at deafening pitches when the zombie jumps out, thereby giving the viewer a heart attack. Authors do not have the luxury of sound effects.*)
That last point is obviously specific to the book I'm reading it, and I only added it because I felt like 5 was a nice, round number. But on that note, my lukewarm response to this book is probably based on a number of factors, many of which may stem from the above multi-MC-based problems, but none of which are unavoidable. That is to say, I'm sure some people can pull off these sorts of books without having these problems.
Just not this author. Or me. Or the author of that other book I read when I was ten and got so, so confused by the fact that I was reading about a different character in every chapter.
Ahem. Anyhow, there's my rambly two cents on the matter.
* Stay tuned for next week's blog post, entitled Why Books Should Have Soundtracks. ;)