Have you ever been able to read one book in three days and couldn’t read another in a week?

This is a difficult question for me, because that's what happens to me. I can read a book in three days, or sometimes in a day, but then I read another one and for some reason I haven't been able to finish it for a month. And no, the book is good, without heavy topics, with a good writing style, but for some reason I'm finishing it until next month. What is the reason for this?