I use my Altered books to progress my collages.
I have found that if I explore and play and move through an altered book project without any judgements on the end results or expectations that even if I make a "mistake" - later on I find it has inspired a whole new wave of creativity and takes on an interesting turn.

You can use an altered book project to move you over a bump in your project, using it as a journal of sorts on the creative process and a sort of blueprint or fancy doodle pad with no limits.