Calling all bookworms! This one's for you.

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Anyone who reads understands the bittersweet feeling of finishing a good book. It’s as if a beloved friend has suddenly packed her things and parted, the back cover swinging closed like a taxicab door. Farewell, friend. See you on the shelf.

If you’ve ever felt weird for considering fictional characters your friends or fictional places your home, science says you no longer have to. A new body of research is emerging to explain how books have such a powerful emotional pull on us, and the answer du jour is surprising—when we step into a fictional world, we treat the experiences as if they were real. Adding to the endless list of reading benefits is this: Reading fiction literally makes you more empathetic in real life.

Not all fiction is created equal, though—and reading a single chapter of Harry Potter isn’t an instant emotion-enhancer. Here are a few key caveats from the nerdy scientists trying to figure out why reading rules.

Rule #1: The story has to “take you somewhere.”

How many times have you heard someone declare that a good book “transports” you? That immersive power that allows readers to happily inhabit other people, places, and points of view for hours at a time is precisely what a team of researchers in the Netherlands credit for the results of a 2013 study in which students asked to read an Arthur Conan Doyle mystery showed a marked increase in empathy one week later, while students tasked with reading a sampling of news articles showed a decline.

Interestingly, several fiction readers who reported that they did not feel “highly transported” by the story also showed a decline in empathy afterward. The takeaway: “A reader has to become fully transported into the story to change as a consequence of reading,” the team wrote. “When readers disengage from what they read, they possibly become more self-centered and selfish in order to protect the sense of self in relation to others.”

In other words, you have to like what you read to reap the social benefits. Anything less, and you’ll just feel grumpy.

Rule #2: One chapter isn’t enough

Emotional intelligence isn’t built overnight. This much became apparent when researchers recently attempted to replicate a reading-empathy study similar to the one above, and failed. (The title of their report was, harshly, “Does reading a single passage of literary fiction really improve theory of mind? An attempt at replication.”)

In their attempt to replicate a well-known 2013 empathy study, researchers had students read either a short passage of literary fiction or non-fiction, then take an empathy test immediately after. While an immediate difference in empathy was visible in 2013, the new paper saw no conclusive evidence that fiction led to emotional intelligence, except for one key factor—how well-read participants were going into the study.

To test a student’s book-worminess, each was given an Author Recognition Test—a common measure of exposure to well-known literature in studies like these—at the start of the experiment. Here’s what the researchers discovered: “The Author Recognition Test, a measure of lifetime exposure to fiction, consistently predicted [empathy test] scores,” their paper says. “The most plausible link between reading fiction and theory of mind is either that individuals with strong theory of mind are drawn to fiction and/or that a lifetime of reading gradually strengthens theory of mind.”

At least for now, the science is in: The more you read, the more your empathy will grow, and the more you’ll love reading. I don’t know about you, but that sounds like the best ‘vicious cycle’ possible.

Get started now: Here are 18 great books you can read in a day.