A generation or two ago, if you needed to quickly understand the plot of a book, you could buy a slender paperback summary from CliffsNotes — at least for the classics commonly taught in high school English classes.

Now, with AI, you can simply upload the book (or an academic paper) to an interface, provided you can find it in PDF form. And thanks to a 15-month-old startup called ChatPDF, you can then ask questions about the book or paper rather than reading it in its entirety.

ChatPDF's product has become popular among students, the company said, and it's easy to see why.

One of the promises of AI is to serve as a "superhero sidekick" that can take on some of the more tedious tasks we don't want to do and free us up to focus our brains on more-substantial work. But generative AI has also made it easier for us to not use our brains at all and lean on chatbots to do most of the heavy lifting. Given the propensity of AI tools to hallucinate, however, plus all the trouble you can get into with plagiarism, you're better off taking the sidekick approach.

Co-founder Mathis Lichtenberger created Berlin-based ChatPDF as "a small AI project" using the ChatGPT API, a few months after the chatbot launched in late 2022. He realized it was now possible to chat with anything — and the simplest use case was a PDF file.

"I was super hyped about AI and wanted to just do a simple product," he said. "I wanted to have something out there, to join the community and get into contact with other people who do other interesting AI stuff."

The typical use case is students and researchers — a user base Lichtenberger didn't envision at the outset.

"We quickly realized it was going super viral among students," he said. "A lot of them use it for academic papers."

To use ChatPDF, you upload a PDF to a window on the site. The chatbot learns about the file and then takes you to a chat interface where you can ask questions. In the case of an academic paper, you could ask about the conclusion or what the paper mentions about a certain topic.

The answers you receive reference the source within the PDF document.

I'm a big John Steinbeck fan, so I uploaded a PDF of his 1937 novella Of Mice and Men to try it out. I asked about the significance of rabbits and was pleasantly surprised.

"Rabbits are a recurring motif that represent Lennie's dream of a better future and his desire for companionship and responsibility," ChatPDF told me. "Lennie's fixation on tending rabbits reflects his innocent and childlike nature, as well as his longing for a simple and fulfilling life on a farm with George."

That's pretty good. But it also offers to rewrite that explanation for me, which seems like a dream come true for a student who waited until the last minute to finish a term paper.

I then asked why the book is called Of Mice and Men and it correctly told me the title refers to a 1785 Robert Burns poem, which says, "The best-laid plans of mice and men / Often go awry."

ChatPDF explained this reflects a central theme, which is the fragility of dreams and the unpredictability of life.

"The juxtaposition of mice, small and vulnerable creatures, with men, who are often seen as powerful and in control, underscores the idea that even the most carefully laid plans can be derailed by unforeseen circumstances," ChatPDF said.

Lichtenberger didn't disclose the exact number of registered users but said it's "a couple of million." However, you can also use the service without signing in, as I did, which also equates to "a couple of million active users" each month, Lichtenberger said. It's not clear what, if any, overlap exists between the two groups.

He was also surprised by the number of global users. (ChatPDF says it accepts PDFs in any language and can chat in any language.)

"Sometimes we have more Spanish speakers than English speakers, and really all over the place, like Chinese and Japanese," he said. "That's something we didn't even think about when we launched the platform." 

While there are potential enterprise use cases, Lichtenberger plans to remain focused on education. ChatPDF has good brand recognition within that space, and the business world is "just a different game to play" and "we would probably have to raise venture capital."

But the tool itself can be used with any PDF, including legal contracts, financial reports and manuals.

ChatPDF was self-funded and is profitable and has no plans to seek funding.

"We will continue to focus on the education space ... and there are some features that we can [add to] make that even more comfortable for them and integrated in the workflow even more," he added.

This is one of a series of short profiles of AI startups, to help you get a handle on the landscape of artificial intelligence activity going on. For more on AI, see our new AI Atlas hub, which includes product reviews, news, tips and explainers.

Editors' note: CNET used an AI engine to help create several dozen stories, which are labeled accordingly. The note you're reading is attached to articles that deal substantively with the topic of AI but are created entirely by our expert editors and writers. For more, see our AI policy.