The English edition of Wikipedia Encyclopedia contains around 3 million articles as of now and if someone were to print the entire Wikipedia encyclopedia into a book, the size of that book would roughly be equivalent to 952 volumes of the Encyclopedia Britannica.
Rob Matthews, a student in UK has actually converted 0.01% of the Wikipedia encyclopedia into a printed book. See some pictures below:
This Wikipedia book has some 5,000 pages and it’s a compilation of 400+ featured articles all picked from Wikipedia. The height of this book is about 1ft 7in.
Thanks to Amit for the pictures.