Both. For cookbooks and anything illustrated, it has to be a physical book. I read a fair amount of books on nutrition,and like them in both forms. Fiction is almost always in ebook form. I read at home,on the bus,on my lunch break,in the park...etc. I've gotten to the stage in life where I don't want to carry anymore than I have to...and adding a book to already bulky/heavy shopping,etc would put me off reading.
I still love physical books and love seeing them in my huge bookcase...finding what I want quickly though,can be an issue.