answer:Mood, balance, and timing. I always have several books on deck. That’s so I’ll have plenty of choice, because I’m never sure what’s next until I finish one. I usually start another immediately—like in the next minute (unless it’s lights-out time)—so it has to be right there within reach. Mood: Sometimes I just can’t face something heavy, and sometimes I want a slow, deep, enriching experience. If I badly need quick escapism, that’s one kind of book. If I want a very satisfying read, that’s another. Balance: I don’t do anything as strict or rigid as alternating genres, but I do vary the mix among fantasy, mystery, realistic mainstream fiction, and experimental novels, and I blend in a fair amount of nonfiction. Fiction may be contemporary or centuries old. Timing: This refers mostly to the fact that I normally have from one to four books out of the library. So I give some priority to whatever is due next. But occasionally I do renew one that I haven’t got to yet, and sometimes I even return books unread. I’m never reading only one book at a time.