Here's the bottom line: if you are unsure whether the book is appropriate for your kids, consult reviewing sources. And. READ. THE. BOOK. My profanity index might not be calibrated the same as yours. Your sense of what might be too dark might differ from mine. Plus, not all readers are calibrated the same way, either. And what I see as educational value might be different as well. So, make up your own mind. You'll know.
Those last two lines above come from Byrd Baylor's EVERYBODY NEEDS A ROCK. I use the story often as a metaphor for selecting books and not rocks. You have to make up your own mind. You'll know.
We need to certainly talk to our colleagues. We cannot read every book (though not a book went on my classroom library shelf that I had not read unless it was in a series as there are only so many Sweet Valley High books one should ever read in a lifetime). But we can use professional sources, especially the standard reviewing journals. We need to be professional; we need to be deliberate; we need to do the work ourselves and not hand decisions over to some program or web site. We have to make up our own minds. We'll know.