Detail that I can't ignore when I see it: "pouring over ABC." You aren't a liquid. That sounds gross. It's "poring over." You're absorbing it, let's say (for the sake of a mnemonic) as if through your pores. That's the expression passed down the generations. Spell-checkers won't catch the error of "pouring" where you should be "poring," though, so it's on you.
Now, to excavate this old metropolitan phrase a little further, the origin of "pore" (this verb we're discussing, meaning "to gaze meditatively") could be a mutation of the verb "peer," which sounds reasonable and likely given the evidence. Or the origin could be the ancient Latin stem for the skin kind of pore, "porus," which means "passage, journey, or way."
If we go with the latter for lack of a definitive answer, then "poring over/through" a spy novel calls to mind absorbing clues through your pores (or sitting, meditatively transpiring through your stomata like a plant?) but on a deeper level could mean "journeying through." One of those two pictures is how I would recommend remembering it if you have trouble, as the image is vivid and points to the right spelling.
With a better lens on the microscope, though, my own interpretation is as likely mistaken as the "pouring" one. It seems the earliest known version, from the 13th century, is "pouren" - without "over" or "through" after it - meaning, basically, "to peer." The skin-type "pore," the noun, only appeared in English a century later, and with the modern spelling, fresh off the chariot from the Latin "porus." Is there time for "porus"-pore to mutate into the differently-spelled and rather different-meaning verb "pouren" when "porus"-pore shows up later in the historical record, not earlier? Probably not.
There's a smoking gun, and it's a verb with no obvious connection to Latin "porus," but a strong connection to looking.
So I'm pretty sure my "absorbing through pores" inference is as off historically (though it gets the spelling right) as "pouring all one's attention over and down the pages." It's really more like "peer deeply."
But if you write "pour over" or "pour through," while this is regarded as incorrect, you can take solace in the etymology pointing to "pouren" - so you might be right after all, even though the word has nothing to do with pouring maple syrup in the cup of tea a waiter just poured for you. However, you might have been poring while he was pouring - hell, maybe you were even poring while you were pouring.
