cannot read one book at a time

i want to stick to one book at a time, but i just can't. i keep telling myself i'll pick one and see it through. i never do. instead, i end up reading three or four books at the same time. i usually have four books in rotation: the current book club pick a fiction novel a classic and a non-fiction book some days i crave the mental challenge. other days i just want to get lost in a story, so i switch to the fiction book. the thing is, i don't like it. i want to immerse myself in one book, finish it, and then move on to the next. but that never seems to happen. i wonder whether my attention span has become that short, or if this is just how i read now.