No. Reading two or three books at once does not, by itself, hurt your memory of any of them. No study has compared whole books read in parallel with books read one at a time, but the closest research points the same way: switching between texts is neither good nor bad on its own. It helps when each switch comes with a recall attempt. Without one, you are just reading more slowly.
If you have several books going:
- Recall before you reopen. When you pick a book back up, close your eyes for two minutes and say where it was: the last argument, what it was building toward, what you expect next. Then open it and check.
- Pair books on purpose. Two books on the same subject if you want to compare them. Books far apart if you read both for the pleasure of it.
- With a similar pair, ask which book said it. Once a week, take one idea and name its source, and where the other book disagrees.
- Keep only as many going as you will actually do step 1 for. That is our rule, not a study’s. If you skip the recall for a book, it has become a book you are merely leafing through.
The rest of this page is the evidence behind those steps, and where it runs out.
Is it bad to read multiple books at once?
Not as far as anyone has shown. The advice you’ll find on this question is mostly preference: some readers love it, some say the books blur together, so pick whatever suits you. That’s fair as far as it goes, but there is research on the mechanism underneath, and it’s more useful than “it depends.”
Reading two books in alternation is a form of what learning researchers call interleaving: mixing different material together (A, B, A, B) instead of finishing one block before starting the next (A, A, B, B). Interleaving has a big reputation, and the biggest review of it is more careful than the reputation.
In Psychological Bulletin (November 2019, volume 145, pages 1029–1052), Matthias Brunmair and Tobias Richter pooled 59 studies and 238 effect sizes (abstract). They found a moderate overall benefit of interleaving (g = 0.42). It was largest for paintings (g = 0.67), typically learning to recognise artists’ styles, and small for mathematics problems (g = 0.34). For expository texts, the kind of nonfiction most readers on this page are juggling, results were “ambiguous with nonsignificant overall effects.” For word lists, blocking actually came out ahead (g = −0.39). The authors’ own conclusion: interleaving “should be used with caution in certain conditions, especially for expository texts and words.”
Two caveats before you take that to your bookshelf. These studies are about learning to tell categories apart, not reading two books in parallel. And “nonsignificant” means no reliable effect either way, not harm. The honest reading is that alternating between nonfiction texts, all by itself, does not buy you much. So whether your parallel reading helps or hurts comes down to what you do at the switch.
What makes switching between books actually work?
Testing yourself at the switch. The clearest text study we found makes the point.
In Advances in Physiology Education (September 2016, volume 40, pages 329–334), Tracy Linderholm, John Dobson and Mary Beth Yarbrough had learners study five physiology texts in four ways (abstract). Some studied each text several times before moving to the next (blocked); others cycled through all five in turn (interleaved). Crossed with that, half simply studied again on each pass and half took a test between passes. Over the following week, the groups that tested themselves “had more stable recall of key text ideas” than the groups that only restudied. Recall of the themes running across the texts was more stable with testing than without it only when the texts had been cycled through in turn.
Notice where the summary puts the benefit. Testing gets the credit for holding on to each text, and testing combined with alternating gets the credit for tying the texts together. Alternating without testing isn’t credited with anything. The usual caveats apply: physiology texts, each studied more than once, and the abstract doesn’t give the full numbers. But it is the closest lab version of a reader with several books going, and it says the switch is where the value is.
There is a second thing a switch does. It puts days between your sessions with each book, so every book in the stack gets read spread out rather than in one go. Whether that spreading helps also depends on starting each session by recalling the last one, which is argued in detail in should you read a book in one sitting or spread it out. Parallel reading gives you that gap automatically. Step 1 is what makes the gap count.
Should you read books on the same subject at the same time?
It depends on what you want from the pair, and the research points in a direction the usual advice doesn’t.
The common tip is to keep parallel books far apart (a novel, a history, a science book) so they don’t blur. Readers do report characters and plots merging when two books are too alike. We found no study that measures this for whole books, so treat it as experience, not a finding. It is a fair reason to choose a far-apart pair when you’re reading for the pleasure of each book.
But Brunmair and Richter found that interleaving helped most when the material was “more similar between categories.” Alternating pays off when you need to tell close things apart. That is exactly the job when you read two books on the same subject: two biographies of the same person, two introductions to economics, a book and its critic. Read side by side, the differences become visible, which is much harder when the first book is three months behind you.
The cost is the one the forum posts describe. Similar books blur unless you keep their sources straight. That’s what step 3 is for. Once a week, take one idea and ask: which book said this, and what does the other one say instead? Answer it without looking, then check. That question does the comparison, and it’s also a recall attempt, which is the part that does the remembering.
So:
- Reading to compare or to understand a subject from two angles: pick a close pair, and quiz yourself on which book said what.
- Reading for the pleasure of both: pick a far-apart pair, and don’t worry about the theory.
Why switching feels less productive than it is
Switching books has a feel to it: each time you return, you’ve lost the thread, and finishing one book before starting the next seems tidier and more efficient.
That impression has been measured, though not with books. In a 2020 study in Memory, Wang, Liu, Xing and Seger asked people to learn painters’ styles in blocks or interleaved, and then asked which way had worked better. Most “reported blocking was more effective, contrary to the reality that interleaving led to the best performance” (abstract). That is paintings, not prose, and it doesn’t prove alternating books works better. It’s a warning about the gut feeling, not a promise. The way to know whether your parallel reading is working is step 1: if you can recall where each book was, it is.
Where Study Junkie fits
The method above costs nothing. The friction is step 1 and step 3: nobody keeps writing good recall questions for three books at once.
Study Junkie turns each book you upload (PDF, DOCX or a text file) into its own course of chapters built from the full text, never a summary. Two books are two courses, and they stay separate in ways that help with parallel reading:
- The tutor only searches that book. Ask a question inside one course and the answer is drawn from that book, not the other one or the internet. Useful when two similar books are starting to blur.
- Recall comes from the chapter you read. Once you switch recall on, marking a chapter as read schedules sessions on days 1, 3 and 7 by default. Each session asks open questions from that chapter, and you check your own answer against the one it reveals.
- The reminder names the book. Each recall email has the book’s title in the subject line, so returning to a book you set down starts with questions on what you last read, which is most of step 1 done for you.
- Practice problems per chapter. Each chapter can generate problems with a tutor that gives hints without handing over the answer.
Two honest limits. There’s no mixed session that pulls questions from several books at once; each recall session is one chapter of one book. And because the tutor only searches the book you’re in, it can’t compare two books for you. Step 3 is still your job.
Verifying your email gives you 1,500 free Study Credits, with no card. After that it’s one-time packs from $10 that don’t expire.
If you would rather do it by hand, the four steps at the top are all there is to it. For what to do after each chapter without a notebook, see how to remember what you read without taking notes. For why recall does more than rereading, see why you forget what you read.
Frequently asked questions
How many books should you read at once? No study gives a number. Our rule is the one in step 4: as many as you’ll actually do a recall for when you return to them. If you’re unsure, start with two. If one book sits untouched for weeks and you reopen it without trying to recall anything first, you’re starting from scratch each time.
Is it OK to read fiction and nonfiction at the same time? Yes, and it’s the easiest pair to run. They’re far apart, so there’s little to confuse, and the novel usually needs no recall routine at all. Save step 1 for the nonfiction book you want to keep.
Does reading several books at once slow you down? Each book takes longer on the calendar, because it shares your reading time. We found no data on total pages read either way. A longer stretch per book is not a loss for memory if each return starts with recall; it’s the spread-out schedule that fades more slowly.
Can one of them be an audiobook? Yes, and that’s a common way to split them: a print book at home, an audiobook on the walk. The recall step matters more for the audiobook, because there’s no page to glance back at. See how to remember what you listen to.