From what I found based in some titles that I have read in the past and in comparison with Blinkist:
- The summaries here feels that has more "meat in the bone" in terms of bring complex ideas and have more bullet points
- Maybe it's about the prompting, but the language used you can definitely know that is generated by an LLM
- Having the direct quotes from the book after an initial definition of the theme of a chapter it's good
- The whole experience with the LLM kicking in on the fly, makes the whole experience quite bad; maybe you should consider have that pre-stored in some place
Honestly, I think your product it's 85% of theirs (and this is not something bad).
The pricing USD 79 for a lifetime it's OK, but without giving some kind of access or even make some library available it's quite hard to see someone paying for a library that you do not know the books that is in there.
From the legal perspective, I think you might be in some hot water since some publishers can dispute the fair use due to the fact that you're monetizing part of their content.