NO definitely NOT in some circles.
YES no problem in others.
And nair the twain shall meet.
Personally I don't, have many songs tucked away back there, which liberal applications of alcohol occasionally free up and they pour forth.
If you HAVE to, I would suggest that you go more for a "card" system, just write the first few words of each verse on a card and keep it hidden under the table or such for when you need it.
If you can't do anything without a book, use it, BUT do not let it affect the quality of performance by sticking your head into it and not interacting with your audience.
I have a friend who is a bit "techy" he uses an "i" thing which gives a wierd illumination to his face in darkened song circles.
JohnB