Uniformity in voice

Have you ever read a book where the voice changes drastically throughout the story making you wonder whose POV you're in? I've read a few, some of them published unfortunately, that do just this. It isn't enough for a book to be good if the voice is different for the same character it isn't good. Conversely if you have different POV in your book, make sure the Voice is Different for each person. The best way I find to do this is to actually read your own work. You know your characters best of all, do them a service by making sure they're three dimensional and having their voice be true to them.