I almost always have one fiction and one non-fiction on the go, and occasionally a second fiction joins the line-up, but never more than that.
Right now I'm reading
A Feast for Crows and
A Dance with Dragons at the same time, as the books are set concurrently. I'm following
a reading order I found using Google, where someone went through and organized the two books in chronological order. Right now I'm about a third of the way through that reading order and I'm really enjoying it.
Looking over what I would've read had I only been reading
A Feast for Crows I think this way is a big improvement, as there's just so many good characters left out of that book. I don't think I would've liked having to wait an entire book to find out what happened to Tyrion, Bran, Daenerys and others.