【Honest Review】What One Month of Using NotebookLM Actually Taught Me
機械翻訳 / Machine-translated
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AI Friends
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機械翻訳 / Machine-translated
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What you'll learn from this article
I needed to read PDF documents and internal files almost every day for work, so I was on the lookout for a summarization tool. I was already using ChatGPT, but repeatedly copying and pasting long PDFs was a hassle, and I kept thinking there had to be an easier way. That's when I came across a post on social media saying "With NotebookLM, you just upload a file and it summarizes it for you," so I decided to give it a try. The fact that it's made by Google gave me peace of mind, and being free to use was another big deciding factor. A major update had just rolled out in June 2026, and I was curious about the new features as well.
My honest takeaway from the first week was simply: "I can't believe how easy this is." You just drag and drop a PDF, and a summary appears within seconds. No technical know-how is required whatsoever — it's simple enough for a middle schooler to use. What I especially loved was a feature called "Audio Overview." It has two AIs explain the content of a document in a conversational format, so I could just pop in my earphones during my commute and absorb the material. The one thing that threw me off was that audio playback would sometimes switch to English when the source material was in Japanese.
1. It only draws from the documents you upload
ChatGPT and other AI tools sometimes blend in information from the internet when generating responses. NotebookLM, on the other hand, uses only the documents you upload as its source, so I felt comfortable using it even with confidential internal materials. Responses also show exactly which page and section they were drawn from, making it easy to verify the source.
2. An impressive range of supported formats
It can handle not just PDFs, but also Word files, Google Docs, YouTube URLs, audio files, and even images. I actually tried uploading meeting minutes (in Word format) together with a YouTube explainer video and had it summarize everything at once — and the result was surprisingly accurate. I felt this kind of flexibility is a genuine advantage that other tools don't have.
3. The free plan is surprisingly capable
Even on the free plan, you can create up to 100 notebooks (think of them like projects), with up to 50 files per notebook. That's more than enough storage for personal use. Audio Overview is also available for free, so being able to try everything without spending a dime was genuinely appreciated.
1. Japanese-language accuracy isn't quite there yet
English documents are summarized with impressive precision, but Japanese documents occasionally produced awkward phrasing. With highly technical materials in particular, there were times it misinterpreted things, so I always had to cross-reference the original document. I'm still a bit hesitant to trust it completely and hand things over without checking.
2. The video overview feature is locked behind a paid plan
I was excited about the "Cinematic Video Overview" feature added in the June 2026 update, but it turned out to be exclusive to the Ultra plan (approximately ¥20,000/month). The fact that Audio Overview is free but the video version suddenly requires an expensive plan was a little disappointing. The barrier to entry is simply too high for an individual to justify.
3. File size limits
There's an upper limit on file size per upload, so very large PDFs — like manuals running hundreds of pages — couldn't be uploaded. In those cases, I had to split the PDF into smaller parts, which added some extra work. Apparently the Plus plan (around ¥2,900/month) relaxes these limits, but for anyone wanting to handle large files on the free plan, it can be a real inconvenience.
Compared to ChatGPT, the biggest difference with NotebookLM is that it only looks at the documents you upload. ChatGPT has a vast breadth of knowledge, but that also means information from outside the documents you care about can sometimes creep in. Using NotebookLM felt like having a dedicated personal assistant who had read only those specific documents — and because the source of every piece of information is clear, the sense of reliability is on a different level. That said, ChatGPT excels at generating text and brainstorming ideas, so knowing when to use each one matters. My personal approach is to use NotebookLM exclusively for "researching and organizing" and ChatGPT exclusively for "thinking and writing."
Who I'd recommend it to
I'd absolutely recommend it to anyone who needs to read large volumes of documents for work or study. It's especially ideal for people handling sensitive information — like internal company documents or academic papers — that they don't want leaked externally. It's also a great fit for people who want to learn by listening during spare moments like a commute. If you're already using Google's services regularly, the integration with Google Docs will feel seamless, so you should be able to hit the ground running.
Who I wouldn't recommend it to
On the flip side, it's not the right tool for anyone looking to use it for purposes beyond document summarization — writing creative pieces, casual conversation, and so on. NotebookLM is, at its core, a "research assistant," which gives it a different role from a general-purpose AI chat tool. Similarly, if you need flawless Japanese-language accuracy, or if you want the video overview feature for free, it may still fall a bit short at this stage.
This article is a cross-post from AI Friends.
