book review: Larry Niven - The Ringworld Engineers

This is the book i've recently read, translated into my native language - lithuanian, of course. This is the sequel to the Ringworld novel, which won both Hugo and Nebula awards. There are further sequels also. So having not read original Ringworld, i still thought The Ringworld Engineers will still be a good reading.
Why haven't i read original novel? Well, because in SF i read what is at hand, what is on a bookshelf in local bookstore, basically not worrying too much whether i am wasting my time. And so often it happens that what others rate high does not impress me and vice versa - so better read random book, and maybe i will discover something wonderful, without apriori judgement. In contrast, regarding professional books (in software engineering, etc), i always choose to read recognized one - maybe because i got sick after reading some books by authors who had no idea what they were writing about, just transcribing what they have read in some manual. I am not kidding, i've seen quite a lot of that kind.
If fact this book was quite a pleasure to read, but still, i thought, could have been better. Nothing to compare to eg Frank Herbert's Dune. I would rate it 4/5. Another thing that bothered me a bit is that there were notably too many grammar errors. My guess is translators were pressed too hard :/
Ringworld is artificial construction - flat ring rotating around the sun in the centre. Its rotation induces gravity-alike force on the inner surface of the circle. All environmental factors are similar to Earth's, and so various hominid species live there. The main point of the novel is that ringworld by itself is not stable - it will eventually collide with the sun. To solve this problem, there were lots of Bussard ramjets on the edge of ringworld, which collect hydrogen from surrounding space as fuel, and can compensate for ringworld's random shifting, 95% of which are now unfortunately gone, and remaining ones are not enough to stabilize ringworld's orbit already. And here our adventure begins - our heroes have to find a way to stabilize ringworld. And that's why i rated this 4/5 - because those adventures, well, could have been more interesting. Regarding ideas - this book is perfect for me. Now our hero is like drug-addict, he stimulates his brain pleasure centre with electric current(another nice idea), and well, seems a little bit detached from the world. Well i dunno, maybe this is because i've read R.C. Wilson's Spin, which was masterpiece in that regard - character's inner universe.
So, my collection of interesting topics from this book (which i will hopefully have a chance to speculate about with my bro, who happens to study physics):

• General ringworld physics - why is it unstable, etc
• Bussard ramjet
• Human evolution, evolution speed
• Stimulating brain pleasure centers with electric current
• Solar flare manipulation via magnetic field, solar flare fo laser
• Superconductors, their usability
• Impact armor, which hardens on impact to protect the wearer