I am a PhD Candidate and fortunate enough to be an author on a technical book. Should I put "PhD Candidate" in the biography? The book will persist forever, but that title will not (presumably, I will graduate).
If you should describe yourself in one or two words (i. e. if the other authors write "professor" or similar), I would not write "PhD candidate" because this does in the view of many readers not sound very competent. Don't describe yourself as someone who hasn't finished something, but rather as someone competent. Write instead i. e. "Jan Gorzny, Gender Researcher". If you should write a longer text about yourself, you can mention this. However, write then also about things you have already achieved (e. g. your masters).