Starting a new read can be tempting. Sometimes I get in the zone, finish a book and get the hankering to begin again. Luckily, I have some form of free will and have the choice to start and finish books as I please, but I have a principle that I like to follow: I don't start books within the same day of finishing one.
Regardless of whether I finished a book within the first hours of waking or if it's the last thing I manage to get done for the day, I hold off and wait at least another day before starting anew. I try to never stretch this rule because I find that reading a book is such an engulfing experience and I like to give myself some time to analyze.
Think about the book as a whole, rather than what was read in your last meeting with it. Remember chapter one, remember those minor characters, remember how the author spoke and things that you found to be original.
When I'm in between texts, I like to take some time to think about the message of the book that I've just read. It's nice to be able to relish in the story because it can help you to look at a book sideways. I find that jumping right into the next story can make its predecessor feel like a fading dream. It can feel like something you know, but can't see.
Having that intermission between subjects gives me time to just think. Even if the past read was a flop, it's just nice to have a break so that you can appreciate what you'll be getting into next time around. I have found that bum-rushing into the next book can be starting off on the wrong foot. Your mind is still thinking about the last thing that you've read and by quickly jumping into the next topic, it gives me this sense of resentment towards what I begin to read.
If I start something new too soon, it can make it harder for me to want to get involved. Personally, the times when I have less space in between texts, the more I tend to stretch out the read because I'm less motivated. Although this is entirely about preference, I think that the idea behind gaining a better understanding of a motive by giving yourself time with it does hold some weight. If you are someone who might describe themselves as bookish, I would recommend giving it a shot.